There are, as we’ve seen, good clinical reasons to start Intermittent Fasting. Some, such as its positive effect on blood markers, should be immediately apparent; others will become manifest over time – a cognitive boost, a self-repairing physiology, a greater chance of a longer life. But perhaps the most compelling argument for many is the promise of swift and sustained weight loss, while still eating the foods you enjoy, most of the time. You may view this as incidental to the plan’s other marked health benefits. Or it may be your primary objective. The fact is you will gain both. Weight loss and better health, two sides of the same page.
Michael’s experience, as described in the previous chapter, will have given you an idea of what to expect. In this chapter I will reveal more detail – explaining how to start, how it will feel, how to keep going and how the central tenets of the Fast Diet can slip easily into the rhythm of your everyday life.
Now, it’s over to you.
Cutting calories to a quarter of your usual daily intake is a significant commitment, so don’t be surprised if your first fast day feels like a tough gig. As you progress, the fasts will become second nature and the initial sense of deprivation will diminish, particularly if you remain aware that tomorrow is another day – another day, in fact, when you can eat as you please.
Still, however you cut it, 500 or 600 calories is no picnic; it’s not even half a picnic. A large café latte can clock in at over 300 calories, more if you insist on cream, while your usual lunchtime sandwich might easily consume your entire allowance in one huge bite. So be smart. Spend your calories wisely – the Menu Plans on pages 139-161 will be useful – but it’s also worth having a clear idea of favourite fast-day foods that work for you. Remember to embrace variety: differing textures, punchy flavours, colour and crunch. Together, these things will keep your mouth entertained and stop it frowning at the hardship of it all.
Animal studies, human studies, research, experiment: as demonstrated in the previous chapter, evidence for the value of fasting is unequivocal. But what happens when you step out of the laboratory and into real life? When and what you eat during your ‘fast’ is critical to the diet’s success. So what’s the optimal pattern?
Michael tried several different fasting regimes; the one he settled on as the most realistic and sustainable is a fast on two non-consecutive days each week, allowing 600 calories a day, split between breakfast and dinner. This pattern has been called, for obvious reasons, a 5:2 diet – five days off, two days on, which means that the majority of your time is spent gloriously free from calorie-counting. On a fast day, he’ll normally have breakfast with the family at around 7.30am and then aim to have dinner with them at 7.30pm, with nothing eaten in between. That way, he gets two 12-hour fasts in a day, and a happy family at the end of it.
The menu suggestions of pages 139-161 are based on this pattern as it is, in his experience, the most straightforward and convincing Intermittent Fasting method.
As will become clear later in this chapter, I found that a slightly different pattern works for me. Sticking to the Fast Diet’s central tenet, I eat 500 calories – but as two meals with a few snacks (an apple, some carrot sticks) in between, simply because the vast plain between breakfast and supper feels too great, too empty for comfort. There is evidence, from trials conducted by Dr Michelle Harvie17 and others, that this approach will help you lose weight, reduce your risk of breast cancer and increase insulin sensitivity.
Which approach is better? At this point, given that the science of Intermittent Fasting is still in its infancy, we don’t know. On purely theoretical grounds, a longer period without food (Michael’s pattern) might be expected to produce better results than one where you eat smaller amounts more frequently. Krista Varady and her team in Chicago have yet to run a study comparing people who consume their calories as a single meal with those who consume smaller meals throughout the day. They are not prepared to speculate on which is better. When we know more we will update you.
Professor Mark Mattson at the National Institute on Aging says that by eating your calories as a single meal you might get a modestly greater ketogenic (‘fat-burning’) effect, compared to three very small meals spread through the day. But he also thinks we shouldn’t get too hung up about it. ‘Regardless of whether the 600 calories is consumed as one meal or two or three smaller meals, you will get major health benefits.’
We await more trials but it is already clear from the hundreds who have tried it that as long as you stick to the Fast Diet you will enjoy that crucial combination of weight loss, health benefits and cheerful compliance.
Some people who don’t feel hungry at breakfast would rather eat later in the day. That’s fine. One of the key researchers in this field often starts her day with a late breakfast at around 11am and finishes with supper at 7pm. That way, she’s fasting for 16 hours a day, twice a week. Based on the mouse study cited on page 28, it may even be a better approach.
It is, however, only better if you actually do it, and a delayed breakfast may not suit some lifestyles, timetables or bodies. So go with a timetable that suits you. Some fasters will appreciate the convenience and simplicity of a single 500- or 600-calorie meal, allowing them to ignore food entirely for most of the day. Whatever you choose, it must be your plan, your life. Do it with gusto, but be prepared to experiment, within the limits set out by the plan.
It may seem curious to talk about what to eat when you are fasting. But the Fast Diet is a modified programme, allowing 500 calories for a woman and 600 for a man on any given fast day, making the regime relatively comfortable and, above all, sustainable over the longterm. So, yes, you do get to eat on a fast day. But it matters what you choose.
There are two general principles that should govern what you eat and what you avoid on a fast day. Your aim is to have food that makes you feel satisfied, but stays firmly within the 500/600 calorie allowance – and the best options to achieve this are foods that are high in protein, and foods with a low glycaemic index (GI). There have been a number of studies demonstrating that individuals who eat a diet higher in protein feel fuller for longer (indeed the main reason why people lose weight on diets like Atkins is because they eat less).18 The trouble with really high-protein diets, however, is that people tend to get bored of the food restrictions and give up.
There is also evidence that high-protein diets are associated with higher levels of chronic inflammation and IGF-1, which in turn are associated with increased risk of heart disease and cancer.19
So the Fast Diet does not recommend boycotting carbs entirely, or living permanently on a high-protein diet. However, on a fast day, the combination of proteins and foods with a low GI will be helpful weapons in keeping hunger at bay.
In earlier chapters, we discovered the importance of blood sugar and insulin. High levels of insulin brought about by high levels of blood sugar will encourage your body to store fat and increase your cancer risk. Another reason not to eat foods that make your blood sugar levels surge, particularly on your fast days, is that when your blood sugar crashes, as it inevitably will, you will start feeling very hungry indeed.
Carbohydrates have the biggest impact on blood sugars, but not all carbs are equal. As habitual dieters will know, one way to discover which carbs cause a big spike and which don’t is to look at their GI. Each food gets a score out of 100, with a low score meaning that the particular food does not tend to cause a rapid rise in blood glucose. These are the ones you want.
The size of the sugar spike depends both on the food itself, and on how much of it you eat. For example, we tend to eat a lot more potatoes in one sitting than kiwi fruit. So there’s also a measure called GL, the Glycaemic Load, which:
GI x grams of carbohydrate
100
This makes some pretty heroic assumptions about the amount of a particular food you are likely to eat as a portion, but at least it is a guide.
The reason GI and GL are interesting is not just because they are strongly predictive of future health (people on a low GL diet have less risk of diabetes, heart disease and various cancers), but because there are so many surprises. Who would have imagined that eating a baked potato would have as big an impact on your blood glucose as eating a tablespoon of sugar?
Broadly speaking a GI over 50 or a GL over 20 is not good, and the lower both figures are the better. It is worth restating that GI and GL are measures that relate to carbs. GI is not relevant to protein and fats, which is why none of the foods listed have a significant protein or fat content. As an example, let’s take a quick look at breakfast:
| BREAKFAST | GI | GL | |
| PORRIDGE | 50 | 10 | |
| MUESLI | 50 | 10 | |
| BAGUETTE | 95 | 15 | |
| CROISSANT | 67 | 17 | |
| CORNFLAKES | 80 | 20 |
Source: http://people.bu.edu/sobieraj/papers/GlycemicIndices.pdf
You can see why, if you are having a carb breakfast, porridge and muesli are better options than cornflakes or a croissant. And what are you going to put on your muesli?
| GI | GL | ||
| MILK | 27 | 3 | |
| SOY MILK | 44 | 8 |
The relatively high GI and GL of soy milk is just one reason to stick with dairy. And since we’re handing out surprises, here’s another one:
| GI | GL | ||
| ICE CREAM | 37 | 4 |
You would bet your house on ice cream being high GI/GL, but not so. If you factor it into your calorie count, low-calorie ice cream with strawberries is a treat to round off a meal. For more on the GI and GL of various foods and how best to plan your fast-day foods, see pages 107-8.
We certainly don’t recommend eating protein to the exclusion of all else on a fast day, but you do require an adequate quantity, for muscle health, cell maintenance, endocrinal regulation, immunity and energy. Protein is satiating too, so it’s well worth including it in your calorie quota. While Valter Longo recommends 0.8g of protein per kg of body weight per day – which would give a 12 stone man around 60g, and a nine-stone woman around 45g – perhaps the simplest method is to stick to recommended governmental guidelines, which allow for a (quite generous) 50g per day.
Go for ‘good protein’. Steamed white fish, for example, is low in saturated fats and rich in minerals. Choose skinless chicken over red meat; try low-fat dairy products over endless lattes; include prawns, tuna, tofu and other plant proteins. Nuts, seeds, pulses and legumes are full of fibre and act as bulking agents on a hungry day. Nuts – though high in calories (depending, of course, on how many you eat) – are generally low GI and brilliantly satiating. They are fatty too, so you might imagine they are ‘bad for you’, yet the evidence is that nut consumers have lower rates of heart disease and diabetes than nut abstainers.20
Eggs, meanwhile, are low in saturated fat and full of nutritional value; they won’t adversely affect your cholesterol levels and they score a mere 85 calories each, so an egg-based breakfast on a fast day makes perfect sense. Two eggs plus a 50g serving of smoked salmon clocks in at a sensible 250 calories. Research recently found that individuals who consume egg protein for breakfast are more likely to feel full during the day than those whose breakfasts contain wheat protein.21 Poaching or boiling an egg avoids the addition of careless calories. Stand down the toast soldiers and replace with steamed asparagus spears. For more suggestions about foods to keep you full and fit on a fast day, and the benefits certain choices will bring, turn to page 107-8.
If you do not have an underlying medical condition, and if you are not an individual for whom fasting is proscribed (see pages 123-4), then there really is no time like the present. Ask yourself: if not now, when? You may prefer to await a doctor’s advice. You may choose to prepare yourself, talk yourself down from a lifelong habit of overeating, clear out the fridge, eat the last cookie in the jar, have a scratch. Or you may want to get on with it and start to see visible progress within a couple of weeks. Do, however, begin on a day when you feel strong, purposeful, calm and committed. Do tell friends and family that you’re starting the Fast Diet: once you make a public commitment, you are much more likely to stick with it. Avoid high days, holidays and days when you’re booked in for a three-course lunch complete with bread basket, cheese board and four types of dessert. Recognise, too, that a busy day will help your fast time fly, while a duvet day generally crawls by like honey off a spoon. Once you’ve deliberated and designated a day to debut, get your mind in gear. Record your details – weight, BMI, target – before you start and note your progress in a diary, knowing that dieters who keep an honest account of what they eat and drink are more likely to lose the pounds and keep them off. Then… take a deep breath and relax. Better yet, shrug. It’s no big deal: you have nothing to lose but weight.
If it has been a while since you have experienced hunger, even the slightest hint, you’ll probably find that eating no more than 500 or 600 calories in a day is a mild challenge, at least initially. Intermittent Fasters do report that the process becomes significantly easier with time, particularly as they witness results in the mirror and on the scales. Your first fast day should speed by, buoyed along by the novelty of the process; a fast day on a wet Wednesday in week three may feel more of a slog. Your mission is to complete it, knowing that, although you are saying no to chocolate today, you will be eating what you want tomorrow. That is the joy of the Fast Diet and what makes it so different from other weight-loss plans.
There is no reason to be alarmed by benign, occasional, short-term hunger. Given base-level good health, you will not perish. You won’t collapse in a heap and need to be rescued by the cat. Your body is designed to go without food for longish periods, even if it has lost the skill through years of grazing, picking and snacking. Research has found that modern humans tend to mistake a whole range of emotions for hunger.22 We eat when we’re bored, when we’re thirsty, when we’re around food (when aren’t we?), when we’re in company or simply when the clock happens to tell us it’s time for food. Most of us eat, too, just because it feels good. This is known as ‘hedonic hunger’ – and while you should try to resist it on a fast day, you can bask in the knowledge that, if you please, you can give in to temptation the following day.
There’s no need to panic about any of this. Simply note that the human brain is adept at persuading us that we’re hungry in almost all situations: when faced with feelings of deprivation or withdrawal or disappointment; when angry, sad, happy, neutral; when subject to advertising, social imperatives, sensory stimulation, reward, habit, the smell of freshly brewed coffee or baking bread or bacon cooking in a café up the road. Recognise now that these are often learnt reactions to external cues, most of them designed to part you from your cash. If you are still processing your last meal, it’s highly unlikely that what you are experiencing is true hunger (‘total transit time’, should you be interested in such things, can take up to two days, depending on your gender, your metabolism and what you’ve eaten).
While hunger pangs can be aggressive and disagreeable, like a box of sharp knives, in practice, they are more fluid and controllable than you might think. You’re unlikely to be troubled at all by hunger until well into a fast day. What’s more, a pang will pass. Fasters report that the feeling of perceived hunger comes in waves, not in an ever-growing wall of gnawing belly noise. It’s a symphony of differentiated movements, not a steady, fearful crescendo. Treat a tummy rumble as a good sign, a healthy messenger.
Remember, too, that hunger does not build over a 24-hour period, so don’t feel trapped in the feeling at any given moment. Wait a while. You have absolute power to conquer feelings of hunger, simply by steering your mind, riding the wave, choosing to do something else – take a walk, phone a friend, drink tea, go for a run, take a shower, sing in the shower, phone a friend from the shower and sing… After a few weeks’ practising Intermittent Fasting, people generally report that their sense of hunger is diminished.
As we’ve seen, one of the key studies to investigate how obese subjects react to Intermittent Fasting was done with volunteers doing the more demanding Alternate Day Modified Fasting method (ADMF) at the University of Chicago. This study found that ‘during the first week of Alternate Day Modified Fasting, hunger scores were elevated. However, after two weeks of ADMF, hunger scores decreased and remained low throughout the rest of the trial’, demonstrating that ‘subjects become habituated to the ADMF diet (i.e. feel very little hunger on the fast day) after approximately two weeks’. Furthermore, ‘satisfaction with the ADMF diet was low during the first four weeks of the intervention, but gradually increased during the last four weeks of the study.’
In short, the researchers concluded that ‘since hunger virtually diminishes, and since satisfaction with diet considerably increases within a short amount of time, it is likely that obese participants would be able to follow the diet for longer periods of time.23 Remember, this research was done with people fasting every other day, something that we both tried and found challenging. By contrast partial fasting two days a week – the Fast Diet plan – is a doddle.
So, take heart. On a fast day, refrain, restrain, divert and distract. Before you know it, you’ve retrained your brain and hunger’s off the menu.
Perhaps the most reassuring, and game-changing, part of the Fast Diet is that it doesn’t last for ever. Unlike deprivation diets that have failed you before, on this plan, tomorrow will always be different. Easier. There may be pancakes for breakfast, or lunch with friends, wine with supper, apple pie with cream. This On/Off switch is critical. It means that, on a fast day, though you’re eating a quarter of your usual calorie intake, tomorrow you can eat as you please. There’s boundless psychological comfort in the fact that your fasting will only ever be a short stay, a brief break from food.
When you’re not fasting, ignore fasting – it doesn’t own you, it doesn’t define you. You’re not even doing it most of the time. Unlike full-time fad diets, you’ll still get pleasure from food, you’ll still have treats, you’ll engage in the regular, routine, food-related events of your normal life. There are no special shakes, bars, rules, points, affectations or idiosyncrasies. No saying ‘no’ all the time. For this reason, you won’t feel serially deprived – which, as anyone who has embarked on the grinding chore of long-term every-day dieting, the kind that makes you want to commit hara-kiri right there on the kitchen floor every time you open the fridge door, is precisely why conventional diet plans fail.
The key, then, is to recognise, through patience and the exercise of will, that you can make it through to breakfast. Bear in mind that fasting subjects regularly report that the food with which they ‘break their fast’ tastes glorious. Flavours sing. Mouthfuls dance. If you’ve ever felt a lazy disregard for the food you consume without thinking, then things are about to change. There’s nothing like a bit of delayed gratification to make things taste good.
Most diets don’t work. You know that already. Indeed, when a team of psychologists at UCLA conducted an analysis of 31 long-term diet trials back in 2007, they concluded that ‘several studies indicate that dieting is a consistent predictor of future weight gain… We asked what evidence there is that dieting works in the long term, and found that the evidence shows the opposite.’ Their analysis found that, while slimmers do lose pounds in the early months, the vast majority return to their original weight within five years, while ‘at least a third end up heavier than when they embarked on the project’.24 The standard approach clearly hasn’t worked, doesn’t work and won’t work.
In order to be effective, then, any method must be rational, sustainable, flexible and feasible for the long haul. Adherence, not weight loss per se, is the key, so your goals must be realistic and the programme practical. It must fit into your life as it is, not the life of your dreams. It needs to go on holiday with you, it needs to visit friends, get you through a boring day at the office and cope with Christmas. To work at all, any weight-loss strategy has to be tolerable, organic and innate, not some spurious add-on that makes you feel awkward and self-conscious, the dietary equivalent of uncomfortable shoes.
While the long-term experience of Intermittent Fasters is still under investigation, people who have tried it comment on how easily it fits into everyday life. They still get variety from food (anyone who’s ever tried to lose weight on ‘only’ grapefruit or cabbage soup will know how vital this is). They still get rewards from food. They still get a life. There is no drama, no desperate dieting, no self-flagellation. No sweat.
Your body is not my body. Mine is not yours. So it’s worth carving out your plan according to your needs, the shape of your day, your family, your commitments, your preferences. We none of us live cookie-cutter lives, and no single diet plan fits all. Everyone has quirks and qualifiers. That’s why there are no absolute commandments here, just suggestions. You may choose to fast in a particular way, on a particular day. You may like to eat once, or twice, first thing or last. You may like beetroot or fennel or blueberries.
Some individuals prefer to be told exactly what to eat and when; others like a more informal approach. That’s fine. It’s enough to simply stick to the basic method – 500 or 600 calories a day, with as long a window without food as possible, twice a week – and you’ll gain the plan’s multiple benefits. In time, there’s little need for assiduous calorie counting; you’ll know what a fast day means and how to make it suit you.
Once you’ve reached your target weight, or just a shade below (allowing room for manoeuvre and a generous slice of birthday cake), you may consider adopting the Maintenance Model. This is an adjustment to fasting on only one day each week in order to remain in a holding pattern at your desired weight, but still reap the benefits of occasional fasting.
Naturally, one day a week – if that’s what you choose – may offer fewer health benefits than two in the long run; but it does fit neatly into a life, particularly if you are not intent on achieving any further weight loss.
Equally, if the beach beckons or there’s a wedding in the diary or you’ve woken up on Boxing Day haunted by that fourth roast potato, step it up again. You’re in charge.
The first thing you can expect from adopting the Fast Diet, of course, is to lose weight: some weeks more, some weeks less; some weeks finding yourself stuck at a disappointing plateau, other weeks making swifter progress. As a basic guide, you might anticipate a loss of around a pound with each fast day. This will not, of course, be all fat. Some will be water, and the digested food in your system. You should, however, lose around ten pounds of fat over a ten-week period, which beats a typical low-calorie diet. Crucially, you can expect to maintain your weight loss over time.
More important than what you’ll lose, though, is what you’re set to gain…
Over a period of weeks, you can expect your BMI, your levels of body fat and your waist measurement to gradually fall. Your cholesterol and triglyceride levels should also improve. This is the path to greater health and extended life. You are already dodging your unwritten future. Right now, though, the palpable changes will start to show up in the mirror as your body becomes leaner and lighter.
As the weeks progress, you’ll find that Intermittent Fasting has potent secondary effects too. Alongside the obvious weight loss and the health benefits stored up for the future, there are more subtle consequences, perks and bonuses that can come into play.
Expect your food preferences to adapt; pretty soon, you’ll start to choose healthy foods by default rather than by design. You will begin to understand hunger, to negotiate and manage it, knowing how it feels to be properly hungry; you’ll also recognise the sensation of being pleasantly full, not groaning like an immovable sofa. Satiated, not stuffed. The upshot? No more ‘food hangovers’, improved digestion, more bounce.
After six months of Intermittent Fasting, interesting things should happen to your eating habits. You may find that you eat half the meat you once did – not as a conscious move, but as a natural one born of what you desire rather than what you decide or believe. You’re likely to consume more veg. Many Intermittent Fasters instinctively retreat from bread (and, by association, butter), while stodgy ‘comfort’ foods seem less appealing and refined sugars aren’t nearly as tempting as they once were. The bag of Haribo in the glove box of the car? Take it or leave it.
Of course, you don’t need to dwell actively on any of this. It will happen anyway. If you are like me, then one day soon, you’ll arrive at a place where you say no to the cheesecake because you don’t fancy it, not because you are denying yourself a treat.
This is the baseline power of Intermittent Fasting: it encourages you to recheck your diet. And that’s your long-haul ticket to health.
So, yes, you’ll start to lose bad habits around food. But if you continue to fast – and feast – with awareness, all kinds of other changes should occur, some of them unlikely and unexpected.
You may, for instance, discover that you’ve been suffering from ‘portion distortion’ for years, thinking that the food piled on your plate is the quantity you really need and want. With time, you’ll probably discover that you’ve been overdoing it. Muffins will start to look vast as they sit, fat and moist, under glass domes in coffee shops. A maxi bag of crisps becomes a monstrous prospect. You may go from Venti to Grande to wanting only half a cup, no sugar, no cream.
Soon, you’ll come to recognise the truth about how you’ve been eating and the wordless fibs you’ve told yourself for years. This is as much a part of the recalibrating process as anything else; you’ve changed your mind. Occasional fasting will train you in the art of ‘restrained eating’; in the last instance, this is the goal. It’s all part of the long game of behavioural change that means that the Fast Diet will ultimately become neither a fast, nor a diet, but a way of life.
After a while, you’ll have cultivated a new approach to eating – thoughtful, rational, responsible – without even knowing you’re doing it.
Intermittent Fasters also report a boost in their energy, together with an amplified sense of emotional wellbeing. Some talk of a ‘glow’ – the result, perhaps, of winning the battle for self-control, or of the smaller clothes and the compliments, or of something going on at a metabolic level that governs our moods. We may not yet know precisely why, but whatever it is, it feels good. Far better than cake. As one online devotee says, ‘Overall, fasting just seems right. It’s like a reset button for your entire body.’25
More subtly still, many fasters acknowledge a sense of relief as their fast days no longer revolve around food. Embrace it. There’s a certain liberty here, if you allow it to materialise. You may find, as we have, that you start to look forward to your fasts: a time to regroup and give feeding a rest.
A lot of men have contacted me over the last few months to let me know how much weight they have lost and also to say how surprised and delighted they are that Intermittent Fasting turns out to be so easy. They like its simplicity, the fact that you don’t have to give things up or try to remember complicated recipes. I also think they rather like the challenge.
The actor and comedian Dom Joly recently wrote that he’d lost two and a half stone after watching my Horizon programme and felt it was an approach he could imagine sticking to for the rest of his life.26 The attraction for him is that he knows he will be able to eat what he wants the following day. He even added that he now rather enjoys the fasting days, something I have heard from a number of men. One of the things that men seem to like particularly about fasting is that they can fit it into their lives with minimal hassle. It doesn’t stop them working, travelling, socialising or exercising. In fact, some find it fuels performance (see page 121 for more on fasting and exercise).
In one Belgian study, men asked to eat a high-fat diet and exercise before breakfast on an empty stomach put on far less weight than a similar group of men on an identical diet who exercised after breakfast.27 This study adds support to the claim that exercising in a fasted state makes the body burn a greater percentage of fat for fuel. At least it does if you are a man.
For me, a fast day now follows a familiar routine. I start with a protein-rich breakfast, normally scrambled eggs or kippers. I drink several cups of black coffee and tea during the day, work happily through lunch and rarely feel any hunger pangs until well into the late afternoon. When they happen, I simply ignore them or go for a brief stroll until they pass.
In the evening I have a bit of meat or fish and piles of steamed vegetables. Having abstained since breakfast I find them particularly delicious.
I never have problems getting to sleep and most days wake up the next morning feeling no more peckish than normal.
While most men I know respond well to numbers and targets (with associated gadgets if at all possible), I’ve found that women tend to take a more holistic approach to fasting. As with much in life, we like to examine how it feels, knowing that our bodies are unique and will respond to any given stimulation in their own sweet way. We respond to shared stories and the support of friends. And, sometimes, we need a snack.
Personally, for instance, I like to consume my fast-day calories in two lots, one early, one late, bookending the day with my allowance and aiming for a longish gap in between to maximise the prospect of health gains and weight loss. But I do need a little something to keep me going in between. A fast-day breakfast is usually a low-sugar muesli, perhaps including some fresh strawberries and almonds, with semi-skimmed milk; there’ll be an apple ‘for lunch’ – hardly a feast, I know, but just enough to make a difference to the day. Then, supper: a substantial, interesting salad with heaps of leaves and some lean protein – perhaps smoked salmon or tuna or hummus – once the kids are in bed. Throughout the day, I drink San Pellegrino mineral water with a squeeze of lime, tons of herbal tea and plenty of black coffee. They just help the day tick by.
In the four months since I started the Fast Diet, I have lost 6kg, and my BMI has gone from 21.4 to 19.4. If you’re struggling with bigger numbers than these, take strength from the fact that heavier subjects respond brilliantly to Intermittent Fasting, and the positive effects should be apparent in a relatively short time. These days, one fast a week (on Mondays) seems to suffice and keep me at a stable, happy weight.
Many women I encounter are well versed in dieting techniques (years of practice), and I’ve found that a couple of tips can come in handy on a fast day. I’d recommend, for instance, eating in small mouthfuls, chewing slowly and concentrating when eating. Why read a magazine, why tweet as you eat? If you’re only getting 500 calories, it makes sense to notice them as they go in.
I have found, like many Intermittent Fasters, that hunger is simply not an issue. For whatever reason – and one wonders whether it suits the food industry – we have developed a fear of hunger, fretting about low blood sugar and whatnot.
On the whole, for me, a day with little food feels emancipating rather than restrictive. That said, there are ups and downs: some days skim by like a stone on water; other days, I feel like I’m sinking, not swimming, perhaps because emotions or hormones or simply the tricky business of life have kicked in. See how you feel, and always give in gracefully if that particular day is not your day to fast.
1. Know your weight, your BMI and your waist size from the get-go. As we mentioned earlier, waist measurement is a simple and important measurement of internal fat and a powerful predictor of future health. People who do Intermittent Fasting soon lose those dangerous and unattractive inches. BMI is your weight (in kilograms) divided by your height (in metres) squared; it may sound like a palaver, and an abstract one at that, but it’s a widely accepted tool for plotting a path to healthy weight loss. Do note that a BMI score takes no account of body type, age or ethnicity, so should be greeted with informed caution. Still, if you need a number, this is a useful one.
Weigh yourself regularly but not obsessively. After the initial stages, once a week should suffice. The mornings after fast days are best if you like to see falling figures. Researchers at the University of Illinois have noted that ‘weight measurements are drastically different from feed to fast day. This discrepancy in body weight is most likely due to the additional weight of food present in the gastrointestinal tract, and not changes in fat mass from day to day. As a potential solution, future trials should average body weight measurements taken from consecutive feed and fast days to attain a more accurate assessment of weight.’28 You might like to do the same, but don’t make weighing – yourself or your calories – a chore.
If you are someone who enjoys structure and clarity, you may want to monitor your progress. Have a target in mind. Where do you want to be, and when? Be realistic: precipitous weight loss is not advised, so allow yourself time. Make a plan. Write it down.
Plenty of people recommend keeping a diet diary. Alongside the numbers, add your experiences; try to note down three good things that happen on each day. It’s a feel-good message that you can refer to as time goes by.
2. Find a fast friend. You need very few accoutrements to make this a success, but a supportive friend may well be one of them. Once you’re on the Fast Diet, tell people about it; you may find that they join in, and you’ll develop a network of common experience. Since the plan appeals to men and women equally, couples report that they find it more manageable to do it together. That way, you get mutual support, camaraderie, joint commitment and shared anecdotes; besides, meal times are made infinitely easier if you’re eating with someone who understands the rudiments of the plot. There are plenty of threads on online chat rooms too. Mumsnet is a great source of support and information. It’s remarkable how reassuring it is to know that you’re not alone.
3. Prep your fast-day food in advance so that you don’t go foraging and come across a leftover sausage lurking irresistibly in the fridge. Keep it simple, aiming for fast-day flavour without effort. Shop and cook on non-fast days, so as not to taunt yourself with undue temptation (For simple, sustaining fast-day recipe ideas, see pages 139-61). Before you embark, clear the house of junk food. It will only croon and coo at you from the cupboards, making your fast day harder than it needs to be.
4. Check calorie labels for portion size. When the cereal box says ‘a 30g serving’, measure it. Go on. Be amazed. Then be honest. Since your calorie count on a fast day is necessarily fixed and limited, it’s important not to be blinkered about how much is actually going in. You’ll find a calorie counter for suggested fast-day foods on page 185. Or download a calorie counter app such as www.myfitnesspal.com. Nutratech.co.uk offers a useful online interactive food diary – go to www.nutratech.co.uk. Alternatively, www.nutritiondata.self.com includes specific search criteria to allow you to match your food choices not only to your calorie allocation but also to your nutritional needs. Way more importantly, don’t count calories on a non-fast day. You’ve got better things to do.
5. Wait before you eat. Try to resist for at least ten minutes, 15 if you can, to see if the hunger subsides (as it naturally tends to do). If you absolutely must snack, choose something that will not elevate your insulin levels. Try some julienned carrots, a handful of plain air-popped popcorn, an apple slice or some strawberries. But don’t pick and peck like a hen through the day; the calories will soon stack up and your fast will be dashed. On fast days, eat with awareness, allowing yourself to fully absorb the fact that you’re eating (not as daft as it sounds, particularly if you have ever sat in a traffic jam popping M&Ms). Similarly, on off-duty days, stay gently alert. Eat until you’re satisfied, not until you’re full (this will come naturally after a few weeks’ practice). Work out what the concept of ‘fullness’ means for you – we are all different and it changes over time.
6. Stay busy. ‘We humans are always looking for things to do between meals,’ said Leonard Cohen. Yes, and look where it’s got us. So fill your day, not your face. As fasting advocate Brad Pilon has noted, ‘No one’s hungry in the first few seconds of a sky dive.’ Engage in things other than food – not necessarily sky diving, but anything that appeals to you. Distraction is your best defence against the dark arts of the food industry, which has stationed donuts on every street corner and nachos at every turn. And remember, if you must have that donut, it will still be there tomorrow.
7. Try the two-to-two: fasting not from bedtime to bedtime, but from 2pm until 2pm. After lunch on day one, eat sparingly until a late lunch the following day. That way, you lose weight as you sleep and no single day feels uncomfortably deprived of food. It’s a clever trick, but it does require a modicum more concentration than the whole-day option. Or perhaps fast from supper to supper, which again means that no day is All Fast and No Fun. The point is that this plan is ‘adjust to fit’. Just like your waistband in three weeks’ time…
8. Don’t be afraid to think about food you like. A psychological mechanism called ‘habituation’ – in which the more people have of something, the less value they attach to it – means that doing the opposite and trying to suppress thoughts of food is a ‘flawed strategy’.29 The critical thought process here is to treat food as a friend, not as a foe. Food is not magical, supernatural or dangerous. Don’t demonise it; normalise it. It’s only food.
9. Stay hydrated. Find no-calorie drinks you like, and then drink them in quantity. Some swear by herbal tea; others prefer a mineral water with bubbles to dance on the tongue, though tap water will do just as well. Plenty of our hydration comes through the food we eat, so you may need to compensate with additional drinks beyond your routine intake (check your urine; it should be plentiful and pale). While there’s no scientific rationale for drinking the recommended eight glasses of water a day, there is good reason to keep the liquids coming in. A dry mouth is the last sign of dehydration, not the first, so act before your body complains, recognising too that a glass of water is a quick way to hush an empty belly, at least temporarily. It will also stop you mistaking thirst for hunger.
10. Don’t count on weight loss on any given day. If you have a week when the scales don’t seem to shift, dwell instead upon the health benefits you will certainly be accruing even if you haven’t seen your numbers drop. Remember why you’re doing this: not just the smaller jeans, but the long-term advantages, the widely accepted disease-busting, brain-boosting, life-lengthening benefits of Intermittent Fasting. Think of it as a pension plan for your body.
11. Be sensible, exercise caution, and if it feels wrong, stop. It’s vital that this strategy should be practised in a way that’s flexible and forgiving. It’s OK to break the rules if you need to. It’s not a race to the finish, so be kind to yourself and make it fun. Who wants to live longer if life’s an abject misery? You don’t want to grunt and sweat under a weary life. You want to go dancing. Right?
12. Congratulate yourself. Every completed fast day means potential weight loss and quantifiable health gain. You’re already winning.
It really doesn’t matter. It’s your life, and you’ll know which days will suit you best. Monday is an obvious choice for many, perhaps because it is more manageable, psychologically and practically, to gear yourself up at the beginning of a new week, particularly if it follows a sociable weekend. For that reason, fasters might choose to avoid Saturdays and Sundays, when family lunches and brunches, dinner dates and parties make calorie-cutting a chore. Thursday would then make a sensible second fasting day, chiming, if such things appeal, with the teachings of the Prophet Mohammed, who is understood to have fasted on the second and fifth days of the week. But be flexible; don’t force yourself to fast when it feels wrong. If you’re particularly stressed, off-colour, tired or peevish on a day that you have designated a fast, try again another day. Adapt. This is not about one-size-fits-all rules; it’s about finding a realistic pattern that works for you. Do, however, aim for a pattern. That way, over time, your fasts will become familiar, a low-key habit you accept and embrace. You may adapt your fasts as your life (and your body) changes shape – but don’t drop too many fast days; there is a danger that you’ll slide back into old habits. Be kind. But be tough.
Fasting for a 24-hour period is practical, coherent and unambiguous, all of which will promise a greater chance of success. It is, however, merely the most convenient way of organising a fast: there’s nothing magical about 24 hours. To save on bother, stick to it, and remind yourself that you’ll be asleep for nearly a third of it.
Most of the studies done to date on humans have involved volunteers fasting on consecutive days; there may be some value in doing back-to-back fasts, but as far as we are aware, there are no studies on humans comparing this approach with split days. We do, however, know what works in practice for many fasters. Michael tried the consecutive system and found it too challenging to be sustainable over time, so he switched to the split version – fasting on Mondays and Thursdays. The weight loss, improvements in glucose, cholesterol and IGF-1 that he saw are all based on this non-consecutive, two-day pattern.
There’s a psychological imperative here too: fast for more than a day at a time, and you may start to feel resentful, bored and beleaguered – precisely the feelings that wreck the best-made diet intentions. A critical part of this plan is that you never feel challenged for long enough to consider quitting. By the time you’ve had enough, breakfast is on the table and another fast has passed.
This will depend largely on your own metabolism, your individual body type, your starting weight, your level of activity and how effectively and honestly you fast. In the first week, you may experience water loss that can account for a significant dip on the scales; with time, your weekly calorie deficit will mean, thanks to the simple law of thermogenics (energy in < energy out = weight loss), that you will be losing fat. Be judicious: abrupt weight loss is not advised and shouldn’t be your aim. You may, however, anticipate losing around half a stone in eight weeks.
As we’ve seen, foods with a low GI or GL will help keep your blood sugar stable, increasing your chances of a successful day with few calories. Vegetables and legumes are, needless to say, amazing, and you should rely on them on a fast day. Packed with nutrients, their bulk fills you up, they have relatively few calories and they keep your blood sugar low. Carrots are a great snack, particularly with hummus dip, which scores an astonishing GI of 6 and a GL of 0. Fruit is handy too, though some fruits are more fast-friendly than others.
Check the GI count of your chosen fast-day foods online. Diabetes UK has an excellent guide at www.diabetes.org.uk.
Or look at the GI Index from the University of Sydney on www.glycemicindex.com, noting that some foods have an unexpected count. Staples, for instance, are worth scrutinising with an eagle eye:
| STAPLES | GI | GL | |
| BROWN RICE | 48 | 20 | |
| WHITE RICE | 76 | 36 | |
| PASTA durum wheat | 40 | 20 | |
| COUSCOUS | 65 | 23 | |
| POTATOES BOILED | 58 | 16 | |
| MASHED | 85 | 17 | |
| FRIED | 75 | 22 | |
| BAKED | 85 | 26 |
The biggest surprise regarding the staples is how big an effect baking or mashing potatoes has on blood sugars. On fast days, avoid these starchy basics, and substitute with plenty of greens. Fill your plate. Watch out for fruit too. Some are your fast friends; others will spike your blood sugar and are best left for the days when you are eating freely.
| FRUIT | GI | GL | |
| STRAWBERRIES | 38 | 1 | |
| APPLES | 35 | 5 | |
| ORANGES | 42 | 5 | |
| GRAPES | 45 | 9 | |
| PINEAPPLE | 84 | 7 | |
| BANANAS | 50 | 12 | |
| RAISINS | 64 | 30 | |
| DATES | 100 | 42 |
Eating the whole fruit will keep you feeling full for longer. Strawberries, without sugar, are extraordinarily low GI/GL and also low calorie (no wonder many fasters eat a bowl for breakfast). The striking thing to note is the high sugar impact of raisins and dates. Avoid them on fast days. For more on calorie levels, refer to the Counter on page 185.
The term ‘super-food’ is more of a marketing ploy than a scientific construct, and clinical nutritionists are loath to use the description. All plants produce a huge range of phytochemicals that can have a beneficial role in the body: eat them on a fast day or, indeed, on any day you please. The following foods taste good and they’re generally low in calories – making them ideal fast-day companions:
Whatever you eat on a fast day (or any day), the most important thing is to relish it. Go slow. Have a look at the menu plans on pages 139-61 for more ideas.
There is some debate as to whether vegetables are best eaten raw or cooked; cooking may, as raw-foodists contend, destroy vitamins, minerals and enzymes, but it also softens cellulose fibres, making nutrients more available for take-up in the body. Lycopene, a potent antioxidant found in tomatoes, is boosted in cooking.39 A small blob of ketchup is no bad thing. Meanwhile, boiled or steamed carrots, spinach, mushrooms, asparagus, cabbage, peppers and many other vegetables also supply more antioxidants, such as carotenoids and ferulic acid, to the body than they do when raw.40 The downside of cooking veg is that it can destroy their vitamin C. The raw versus cooked argument is a complicated one. Our best advice? Eat plenty of vegetables, just the way you like them.
Yes. Counter-intuitive as it may seem, no foods are off-limits, none proscribed. On the five days a week when we’re not restricting calories, we both eat freely – fish and chips, roast potatoes, biscuits, cake. The Illinois study certainly found that volunteers encouraged to eat lasagne, pizza and fries during ‘off days’ still lost weight.
Even so, don’t try to gorge in a bid to make up for lost time, like a contestant in a blueberry pie contest. You could compensate for fasting by grossly overeating the next day, but it’s very hard to do and you probably won’t want to; a calorie slash of 75% on a fast day generally gives rise to little more than a 15% increase on the following feed day.
This absence of hyperphagia (excessive appetite) on a non-fast day surprised the research team: ‘We hypothesised that the participants would increase their energy intake on the feed day by approximately 125% of their baseline needs. However, no such hyperphagic response was observed… On average, subjects were only consuming 95(±6)% of their calculated energy needs on the feed day. This change in meal pattern helped these subjects to achieve a marked degree of energy restriction (37% net daily), which was related to the pronounced weight loss attained (5.6kg in eight weeks). These preliminary data suggest that subjects are not likely to consume higher fat diets on the feed day when partaking in an ADMF regimen.’41
Humans have, however, evolved to prefer calorie-rich foods – it once gave us an edge – and perhaps the greatest advantage of the Fast Diet is that it expressly includes ‘pleasure foods’, on five days of the week. For most of the time, there is no limitation, no deprivation, no guilt. The psychological impact of not being denied is huge; it frustrates what’s known as the ‘disinhibition effect’ – a paradox in which designating certain foods ‘off limits’ makes us likely to eat more of them.42
Remember, then, that this is not a cycle of bingeing and starving: it is calibrated and moderate. Studies and experience show that Intermittent Fasting will regulate the appetite, not make it more extreme. You could pig out on your non-fast days, working your way steadily through all the ice-cream flavours in the freezer. (Even if you did, you’d still get some of the metabolic benefits of fasting.) But you won’t do that. In all likelihood, you’ll remain gently, intuitively attentive to your calorie intake, almost without noticing. Similarly, you may find yourself naturally favouring healthier foods once your palate is modified by your occasional fasts. So, yes, eat freely, forbid nothing, but trust your body to say ‘when’.
Dieting lore has long suggested that breakfast is the most important meal of the day – miss it in the morning and it’s like leaving the house without a coat. But that’s not necessarily the case. Recent research shows that a bigger breakfast begets a bigger lunch (and a bigger dinner), which – no surprises here – means a higher overall calorie count for the day.43 Some fasters find that they need sustenance to start the day, others may prefer to wait until later to ‘break their fast’. It’s up to you, and whichever pattern you choose may change over time.
Plenty – as long as it doesn’t have a substantial calorie content. In practice, as with most decisions on the Fast Diet, the choice is entirely up to you. Drink plenty of water – it’s calorie-free, actually free, more filling than you think and will stop you confusing thirst for hunger. In summer, add rounds of cucumber or a dash of lime. Freeze it and suck on cubes. If you want warmth, miso soup contains protein, feels like food and clocks up only 84 calories per cup; vegetable bouillon pulls off the same trick. If you find it hard to sleep, a mug of instant low-cal hot chocolate is under 40 calories and a comforting thought.
During the day no-cal drinks are best. Hot water with lemon is a standby favourite for fasters, but you might prefer to add mint leaves or a scattering of cloves, a slice of ginger root or some lemongrass. If you are fond of herbal teas, try some unfamiliar flavours to spice up the day (liquorice and cinnamon, lemon grass and ginger, lavender, rose and chamomile…) Green tea may have health-giving antioxidant properties (the jury’s out), but if you like it, drink it.
On fast days we drink our tea and coffee black and sugarless; if you prefer it with milk and artificial sweeteners, fine. But beware that the calories in milk add up, and what you are trying to do is extend the time you are not consuming any calories at all.
While fruit juices are seen as healthy, they generally have a surprisingly high sugar content, are lower in fibre than a whole fruit and can rack up the stealth calories without so much as a by-your-leave. Commercial smoothies can have a similar sugar content to Coke and, because they are acidic, they are corrosive to your teeth; they are also loaded with calories. If you need flavour, swap juice and smoothies for very dilute cordials – perhaps a dash of elderflower with fizzy water and lots of ice.
Alcoholic drinks, though pleasant, merely provide ‘empty’ calories. One glass of white wine contains about 120, while a 550ml can of beer has 250. Unless you really can’t say no, abstain absolutely on a fast day – it’s a golden opportunity to slash your weekly consumption without feeling serially deprived. Think of it as an alcovoid, for two achievable days each week.
There’s a growing body of evidence to suggest that – far from being a guilty pleasure – drinking coffee may be good for you, helping to prevent mental decline, improve cardiac health and reduce the risk of liver cancer and stroke.44 So go ahead, drink coffee if that’s what gets you going and keeps you going each day. It’s a useful weapon in your arsenal against boredom, and coffee breaks can pleasantly punctuate your day. There’s no metabolic reason to avoid caffeine during a fast, but if you have trouble sleeping, limit your intake later in the day. You should, of course, drink it black. A 16 fl oz caramel macchiato has 224 calories… Just saying.
The general idea of the Fast Diet is to give your body an occasional holiday from eating. Let your mouth rest. Give your belly a break. If you must snack on a fast day, do it with awareness and frugality, always keeping a weather eye on the GI:
| GI | GL | ||
| NUTS | 27 | 3 | |
| POPCORN | 72 | 8 | |
| RICE CAKES | 80 | 19 | |
| FRUIT BARS | 93 | 20 | |
| MARS BAR | 65 | 26 |
You knew that chocolate bars were hardly a health food, but did you know how sugary rice cakes and fruit bars can be? Bear in mind that processed foods tend to have hidden sugars and, though convenient, won’t give you anything like the nutritional advantage of good old-fashioned plants and proteins. Try carrot or celery sticks with hummus, or a handful of nuts – always factoring them into your daily calorie count (don’t cheat).
Habitual snacking, even on low-calorie, nutrient-rich foods, is not advised; part of the motive here is to retrain your appetite, so don’t overstimulate it. If your mouth is desperate for attention, give it a drink.
A number of people say that commercially available meal-replacement shakes helped them through the first, and normally hardest, weeks of an intermittent fast. Arguably, shakes are simpler than calorie-counting, and on your fast day you could simply sip away when waves of hunger strike. We are not great fans as we think real food is better. But if you find it helps, by all means try it. It’s best to go for brands that are low in sugar.
To clarify: this is a book about fasting, the voluntary abstention from eating food. The reasons why this is good for you go way beyond the fact that you are simply eating fewer calories. They arise because our bodies are designed for intermittent fasts. As you’ve seen, the scientific term is hormesis; what does not kill you makes you stronger. So while starvation is bad, a little bit of short, sharp, shock food restriction is good.
Your aim, then, is to carve out a food-free breathing space for your body. Going to 510 calories (or 615 for a man) won’t hurt – it won’t obliterate a fast. Indeed, the idea of slashing calories to a quarter of your daily intake on a fast day is simply one that has been clinically proven to have systemic effects on the metabolism. While there’s no particular ‘magic’ to 500 or 600 calories, do try to stick resolutely to these numbers; you need clear parameters to make the strategy effective in the medium term.
Having ‘an extra cookie’ on a fast day would be antithetical to your goals (not to mention the fact that it would probably spike your blood sugar and eat up most of your allowance in one buttery bite); when you’re fasting, you need to think sensibly and coherently about your food choices, following the plan laid out here. Exercise will-power, reminding yourself that tomorrow is on its way.
The Fast Diet is an intermittent method, not a deprivation regime, so your nutritional intake from a wide variety of food sources should remain relatively steady over time, providing all the vitamins and minerals you require. If, as recommended, your fast-day foods centre on protein and plants, they’ll give you all the goodness you need so you won’t have to resort to costly bottled multivitamins. Do, however, choose your fast-day foods with care, ensuring that, over the course of a week, you consume adequate B vitamins, omega 3s, calcium and iron. Be sensible and eat well. While we are not fans of bottled vitamins and minerals, if a qualified health professional has suggested a particular supplement, you should continue to take it.
Why not? In the interests of flexibility and normality, there’s no reason to change your usual pattern of activity while fasting. Research demonstrates that even a more extreme three-day total fast has no negative effect on the ability to perform short-term, high-intensity workouts or long-duration, moderate-intensity exercise. Athletes seem to suffer no loss in performance during occasional fasting; a 2008 study of Tunisian footballers during Ramadan found that fasting had no effect on performance (‘Each player was assessed for speed, power, agility, endurance, and for passing and dribbling skills. No variables were negatively affected by fasting.’)45 In fact – and this is worth noting if you are aiming for optimal fitness – training while fasting can result in better metabolic adaptations46 (which means enhanced performance over time), improved muscle protein synthesis,47 and a higher anabolic response to post-exercise feeding.48, 49
Training on an empty stomach turns out to be beneficial on multiple levels, coaxing the body to burn a greater percentage of fat for fuel instead of relying on recently consumed carbs; if you’re burning fat, don’t forget: you’re not storing it. As we’ve seen, one recent study found that working out before breakfast is beneficial for metabolic performance and weight loss.50 A report in The New York Times suggests that it even ‘blunts the deleterious effects of over-indulging’ – making fasted exercise a canny way of ‘combating Christmas’.51 According to the study’s authors, ‘Our current data indicate that exercise training in the fasted state is more effective than exercise in the carbohydrate-fed state.’ Certainly food for thought. Do not, however, increase your fast-day food allowance to ‘compensate’ for calories burned through exercise: on a fast day, stick to 500 or 600 calories, whatever level of activity you choose. That’s where the benefits lie.
Clearly, men and women have metabolic and hormonal differences; for evolutionary reasons, we store and utilise fat in different ways. Women carry more fat, are better at storing it and tend to be more efficient at burning fat in response to exercise.52
Though few studies have been done, there’s some evidence to suggest that fasting women have a better response to endurance training than weight training,53 while men may fare better with weights. Anecdotally, men tend to find working out on an empty stomach easier to accomplish than women.
In terms of general health, the benefits of occasional, short-term fasting for both sexes are pretty clear. Although quite a few studies have been done with male volunteers, others have been done with a mixed group or mainly female volunteers. Those in Krista Varady’s studies have been almost all women; Michelle Harvie’s volunteers, all women. Their results are striking and positive; nevertheless, further trials are required to analyse the precise effects of fasting on hormones, particularly among women of different ages. As with all recommendations in this book, be cautious and self-aware. This is not meant to be a struggle; it’s intended as a well-marked route to good health. If, for whatever reason, short bouts of fasting interrupt your cycle or your sleep pattern, modify your approach till you find a comfortable balance that works for you.
The science is still unfolding, and there haven’t been enough clinical trials to assess the overall effects of fasting on fertility. According to Professor Mark Mattson, an Intermittent Fasting plan, such as the Fast Diet, will not affect fertility. More extreme fasting may. It does in animals, but in a reversible manner. Nonetheless, we err on the side of caution and suggest that if you are trying to get pregnant, you should not fast. Period.
You should certainly not fast if you are already pregnant. Pregnant women should eat according to government guidelines and not limit their calorie intake.
There are certain groups for whom fasting is not advised. Type 1 diabetics are included in this list, along with anyone suffering from an eating disorder. If you are already extremely lean, do not fast. Children should never fast; they are still growing and should not be subject to nutritional stress of any type. If you have an underlying medical condition, visit your GP, as you would before embarking on any weight-loss regime.
If you do, it may be due to dehydration rather than a lack of calories. You might experience mild withdrawal symptoms from sugar (or caffeine if you’ve dropped it), but the brevity of your fast shouldn’t make this of particular concern. Keep drinking water. Treat a headache as you would normally; if fasting today is making you feel particularly unwell, stop. You are in charge.
If in reasonable good health, your body is a remarkably efficient and functional machine, capable of – in fact, designed for – the effective regulation of blood sugar. Short-term fasting is unlikely to yield a hypoglycaemic response. The recently propagated idea that we need to graze to avoid a ‘blood sugar crash’ is a myth; if you follow the guidelines set out here and eat low-GI foods on a fast day, your blood glucose should remain stable. But don’t overdo it. If you fast for extended periods, longer than the bi-weekly, 24-hour modified eating programme recommended here, you may experience a drop in blood pressure, a drop in glucose levels and dizziness. So, fast smart. If you are diabetic, consult your doctor before embarking on any dietary change.
The Illinois researchers hypothesised that subjects would feel ‘less energetic on fast days, and would therefore be less physically active’.54 They found no such thing, which suggests that short-term, deliberate, modified fasting will not leave you beat. As in normal life, you’ll undoubtedly have up days and down days, good days and bad. Anecdotally, many Intermittent Fasters we have encountered report a boost in energy rather than a depletion. See how you fare. You may find that a fast day ends earlier than usual – no alcohol and plentiful sleep being a great way to arrive at breakfast sooner.
Probably not, though it will depend on your particular metabolism, and how you timed your fast-day calorie consumption. If you feel hungry, take your mind off it – a bubble bath, a good book, a stretch out, a herbal tea. Get psychology on your side: congratulate yourself on reaching the end of another fast day. Surprisiingly, perhaps, fasters report that they don’t wake up ravenous and run to the fridge as soon as the alarm goes off. Hunger is a subtle beast, and your appetite will soon find its rhythm.
Since you’re not restricting calories every day, your body will not enter the fabled ‘starvation mode’. Your fasting will never be intense. It will only ever be conservative and short-lived, so while your body will burn energy from its fat stores, it will not consume muscle tissue. Research has shown that occasional fasting does not suppress the metabolism.55 Even extreme fasting – an absolute fast for three consecutive days56 or on every other day for three weeks57 – generates no decrease in basal metabolic rate. Nor does Intermittent Fasting raise levels of the hunger-stimulating hormone ghrelin. Researchers at Pennington Biomedical Research Center in Louisiana found that ‘ghrelin was unchanged in both the men and the women, even after 36 hours of fasting’.58 If you follow the moderate, judicious approach advised here, a short window without food is a scientifically sanctioned path to health and wellbeing.
Participate, but with a nonchalant awareness. While support from family and friends is an asset, making a song and dance about your fast will only cause you to feel self-conscious, turning the diet into an obstruction, a hurdle, rather than something that should slot happily and calmly into your life. Remember your trump card: you’ll eat normally again tomorrow. Some days, of course, are tougher than others. As Dr Varady noted among her trial subjects, hunger spiked at week eight: ‘We speculate that this may have occurred because this study week corresponded to Memorial Day weekend, and subjects may have felt hungrier while attending food-related celebrations.’59
If you know that you have a social event – or a food-related celebration – in the diary, fast the day before or the day after. The flexibility of the plan explicitly means – in fact, it demands – that you still go to that wedding, birthday, anniversary dinner, christening, bar mitzvah, supper date, posh restaurant. Take a break for Christmas, Easter, Thanksgiving, Diwali. Yes, you may well put on a little weight, but this is a life, not a life sentence. You can always deviate, eat chips and dips and things on sticks, and then revert to more challenging fasting once the party’s over.
Clinical trials have concluded that Intermittent Fasting is a sustainable – indeed, one of the most effective – ways for obese individuals to lose weight and keep it off; the larger you are, the greater your initial weight loss is likely to be. If you are obese it’s likely that, for whatever reason, traditional restrictive diets have failed for you. The Fast Diet is different because of its flexibility, its war on guilt, and its express approval of ‘pleasure foods’ on non-fast days. The Illinois studies have shown that obese people were able to quickly adapt to ADF. They were also able to maintain physical activity despite fasting. In conclusion, ‘overweight and obese patients appear to experience significant improvements with IF regimes’.60 As with any underlying medical condition, we recommend that you fast under supervision.
There’s no reason not to; that is, after all, what Dr Krista Varady’s ADFs (Alternate Day Fasters) effectively do. However, beware ‘fast fatigue’. One of the keys to its success is that the Fast Diet requires only short-lived dedication. Ask your body to do more than that and it may revolt and refuse to behave, making the recommended fasting programme harder to achieve. Experience tells us that two days is enough. But if you have a date and a small pair of party pants on standby, an occasional, single sneaky extra day shouldn’t hurt. Don’t, however, try a lengthy crash diet. Unless you are obese and it is medically supervised, it just isn’t worth it.
If you are already at a reasonable, happy weight, you can still fast effectively, but consider adapting your consumption on non-fast days to encompass more calorie-dense foods. The main researchers we talked to in this field are all slim and they still fast. With practice, you will discover an amicable balance between fasting and feeding which keeps your weight in the prescribed range. Fast once a week, rather than twice a week. There have been no specific studies to illuminate the effects of doing this, but use your common sense and watch the scales; don’t slide. As mentioned above, if you are already extremely lean or suffering from an eating disorder, fasting of any description is not advised. If in doubt, see your GP.
On the contrary, there’s no time to lose. The Fast Diet is likely to prolong your life. It will moderate your appetite and help you lose weight. Its effects are quickly felt, often within a week of starting your simple bi-weekly mini fasts. It all points to a healthier, leaner, longer old age, fewer doctors’ appointments, more energy, greater resistance to disease. Our advice? Start yesterday.
Interestingly, the Fast Diet’s on/off eating scheme looks a lot like the approach of many naturally slim people. Some days they’ll pick, other days they’ll tuck into treats. In the long run, this is how the Fast Diet goes. As you settle into the routine, you’ll naturally moderate your calorie intake on fast days and feed days, until the process is innate. When you reach your target weight, you can change the frequency of your fast. Play with it. But don’t drift; stay alert. Your aim is a permanent life change, not a blip, not a fad, not a dinner-party chat. This is a long-distance route to sustained weight loss. Accept that it is something you will do, in a form that suits you, indefinitely. For as long as life.
Fasting, as we mentioned at the beginning of the book, has been practised for many thousands of years and yet science is only just starting to catch up. The first evidence of the long-term benefits of calorie restriction were found just over 80 years ago, when nutritionists working with rats at Cornell University in the US discovered that if you severely restrict the amount they eat, they live longer. Much longer.
Since then, the evidence has continued to mount that animals not only live longer, healthier lives if they are calorie-restricted, they also do so if they are intermittently starved. In recent years the research has moved on from rodents to humans and we are seeing the same patterns of improvement.
So where do we go from here? Professor Valter Longo, who has done so much pioneering work with IGF-1, is running a number of human trials in conjunction with colleagues at the University of Southern California, looking at the impact of fasting on cancer. They have already demonstrated that fasting will cut your risk of developing cancer; now they want to see if fasting will also improve the efficacy of chemotherapy and radiotherapy.
Dr Krista Varady of the University of Illinois in Chicago has a number of projects planned. She has a trial running at the moment looking at how well people are able to tolerate ADF in the long run. This is critical research because the success or otherwise of a dietary intervention depends entirely on compliance. Will people stay on it? Last time we spoke, she was also bubbling with ideas for the future, including investigations into why people on ADF lose fat but don’t seem to lose significant muscle mass, and why people on ADF don’t seem to fully compensate for the calories they’ve missed by eating more on their feed days. She has many theories but needs more cold hard facts.
Professor Mark Mattson of the National Institute on Aging in Baltimore is adding all the time to the dozens of research papers he has already published on the effects of fasting and Intermittent Fasting on the brain. We are particularly interested to see the outcome of some of his current studies, which include looking further into what happens to the brains of volunteers when put on an Intermittent Fasting regime.
In addition, his team is looking at drug therapies, as they know that despite the benefits, many people may not want to fast. So they are, for example, investigating a drug called Byetta, used for the treatment of diabetes, but which also seems to activate the production of BDNF (brain-derived neurotrophic factor). This in turn, as we’ve seen, seems to protect the brain against the ravages of ageing. The hope is that Byetta or a related drug will, if not prevent dementia, at least slow its progression significantly.
Intermittent Fasting has, until now, been one of the best-kept secrets in science. We look forward, with a great deal of personal interest, to seeing how this particular story unfolds.