When it comes to health and wellness, there’s a reason we look to the accuracy and authority of scientific experiments to help us suss out what’s truly useful and sound information from all of the baseless, specious, and fad claims and advice out there—to separate the proverbial wheat from the chaff: Scientific experiments aren’t based on hype and hope.
A well-designed, well-conducted scientific experiment helps separate truth from wishful thinking, fact from fantasy. And a series of scientific experiments, testing the same theory and generating the same results (what scientists call replicating a scientific finding), creates a body of knowledge you can trust and then act on.
Given the importance of weight loss to our health and well-being, to preventing and reversing disease, and to restoring self-esteem, you’d think most diet books would be packed with scientific evidence that justifies their approach. But that’s not the way it is.
Yes, there have been scientific studies on a few popular diet plans. For example, a study published in the Journal of the American Medical Association showed that overweight and obese women on the Zone Diet, the low-carb Atkins Diet, or the low-fat Ornish Diet lost a little bit of weight after one year of dieting—an average of 3.5 pounds on the Zone Diet, 4.8 pounds on the Ornish diet, and 10.4 pounds on Atkins.1 (Yes, that’s after dieting for one year. I think you’ll do a lot better on the Every-Other-Day Diet.) However, most popular weight-loss plans don’t have any scientific support for their approach. None. Zero. Zilch.
Why am I making such a big fuss over scientific support for the diet plans in diet books? Because the Every-Other-Day Diet does have a significant body of scientific research behind it. To date, I’ve conducted seven clinical trials involving nearly 400 people, and I have published the results in 20 scientific papers. My studies have shown, again and again, that the Every-Other-Day Diet works. The people in my studies lose weight. And in my ongoing, three-year study on weight maintenance sponsored by the National Institutes of Health, EOD dieters are keeping the weight off.
In other words, the Every-Other-Day Diet is a research-proven diet that you can trust. If you follow this diet, eating 500 calories on Diet Day and whatever you want on Feast Day, the scientific evidence says you will lose weight. And if you go on the maintenance program described in chapter 7, the Every-Other-Day Success Program, my newest findings show you will keep the weight off.
I know the Every-Other-Day Diet may seem too good to be true. I know you might be asking yourself, “Can I really lose weight eating anything I want, every other day?” Never fear. You can. And not just because I say so—because nearly a decade of rigorous scientific research says so. And since your trust in the science-proven effectiveness of the Every-Other-Day Diet is so important to me, I’ve devoted this chapter to sharing the research and studies that support my claims. I want you to know—really know—that the diet you’re about to undertake isn’t a novel idea that’s never been put to the test. It’s not based only on the experience of patients in one doctor’s practice (which is the case with many diet plans). And it’s not theoretical—an idea that seems to make metabolic and biological sense, but has little real-world evidence to show that it works.
By learning about the science of every-other-day dieting and by reading about my studies and their positive findings, you can embark on this new weight-loss program with confidence, conviction, and enthusiasm. So let’s start at the beginning: with my discovery of this diet, in the basement of a building on the campus of the University of California, Berkeley, where, in 2006, I was a postdoctoral fellow.
After I graduated from McGill University in Canada with my PhD in nutrition, I moved to California to do postdoctorate research in the Department of Nutritional Science at Berkeley. (A native Canadian, I was delighted to discover that “winter” in Northern California is just a series of rainstorms and that daffodils bloom in February!)
Under the guidance of my advisor, Dr. Marc Hellerstein, I investigated the effect of calorie restriction on cancer. There was already a lot of research on calorie restriction and longevity in animals; it showed that when mice are fed less food, they live up to twice as long as mice fed a normal diet. Furthermore, some of the biochemical mechanisms triggered by calorie restriction in longevity research are known to be anticancer. The mechanisms include slower cell division; lower levels of IGF-1 (insulin-like growth factor 1, a growth factor that stimulates cancer cells to divide and multiply); and lower levels of glucose, the main fuel for cancer cells.
Our research question was this: Can you put a mouse on the ultimate form of calorie restriction—fasting—so that the growth of cancer cells is slowed, but the animal does not lose weight? (In their research, scientists are always trying to isolate and analyze specific factors. In this case, we wanted to isolate the effect of calorie restriction on cancer from the effect of weight loss on cancer.)
But as hard as we tried, we couldn’t keep the mice from losing weight! We fasted them one day and let them eat all they wanted the next day. But they never ate enough calories on “feed day” to fully compensate for the total lack of calories on “fast day.” Sometimes they managed to eat 150% of a normal day’s calories on feed day. Sometimes they ate up to 170%. But they never ate 200% of their normal caloric intake on feed day to make up for the zero calories on fast day. And so they always lost weight.
My experiment had failed because there was no way to separate the effect of calorie restriction from the effect of weight loss. I was not a happy scientist! But a scientific investigation that seems like a dead end can suddenly present a new vista of opportunity. And that’s just what happened: I had a eureka moment, an Aha!, a conceptual breakthrough when I realized that the mice always lost weight on alternate-day fasting. The mice always lost weight. Could alternate-day fasting help us humans lose weight? If people fasted one day and then ate all they wanted the next day, would they always lose weight, just like the mice?
The concept of the Every-Other-Day Diet—using alternate-day fasting for weight loss—was born. It was time for me to say good-bye to the mice in the basement at Berkeley and move to Chicago, where I had been hired as an assistant professor in the Department of Kinesiology and Nutrition at the University of Illinois at Chicago. There, I started conducting studies on weight loss. With people.
When I looked closely at the scientific literature on alternate-day fasting for cancer and heart disease—studies conducted exclusively on animals in the laboratory—I found that many of the risk factors for the two diseases were lowered most effectively when the animals ate only 25% of their normal calories on fast day. Not 75%. Not 50%. Not 0%, or a total fast. Time and again, the healthiest percentage was 25%, or what I call a modified fast.
And the 25% level of calories on fast day did more than prevent and reverse signs of disease. It also prevented the loss of muscle mass the animals otherwise had experienced at 0%, when they were given no food on fast day.
Why was that important? Losing muscle mass while dieting is a disaster for weight loss and weight maintenance. That’s because muscle (lean body mass, in scientific terms) is metabolically active tissue that burns a lot of calories. Lose muscle during dieting and you’ll burn fewer calories after dieting and regain your weight—as fat! This is perhaps the key reason why 5 out of 6 people who lose weight gain it all back (and then some). So I decided that on fast day—the day called Diet Day in the Every-Other-Day Diet—people would eat 25% of their normal caloric intake, or about 500 calories. I was ready to recruit participants and begin my study.
At this point, I have to make an embarrassing confession: even though I was about to conduct a study on every-other-day dieting in people, I didn’t think the diet would work!
Why not? Well, many overweight people eat around 3,000 calories a day, and I couldn’t imagine they’d be willing or able to eat only 500 calories every other day. And then there was my conversation at a medical conference with Dr. Eric Ravussin, PhD, director of the Nutrition and Obesity Research Center at the Pennington Biomedical Research Center at Louisiana State University. I told him I was thinking of conducting a study on alternate-day fasting for weight loss, allowing my participants to eat 500 calories on fast day.
“Don’t even bother,” he said. And then he proceeded to tell me (to my surprise) that he and his colleagues had recently conducted a human study on alternate-day fasting, in which the participants ate zero calories on fast day. A study that didn’t go too well.2 First, he wasn’t able to recruit anyone from outside Pennington to participate in the study, because the idea of fasting every other day seemed so onerous; he was forced to enroll Pennington professors in the study. Next, he couldn’t even convince many of those professors to participate for all three weeks of the study. Of the 16 that started, only 8 finished. And even those who finished told him they hated alternate-day fasting. Their families hated it, too. “I was so cranky and irritable on fast day that my wife wouldn’t talk to me,” said Dr. Ravussin, who participated in his own study.
I had already planned to allow my study participants to eat 500 calories on fast day; my conversation with Dr. Ravussin convinced me I’d made the right decision. For successful every-other-day dieting, you need to be on a modified fast, not a total fast. (In scientific papers, I sometimes call my approach ADMF, or alternate-day modified fasting.) You need to eat a small meal during the day, so you can stay balanced emotionally and mentally, interact with people without blowing a fuse, and get through your workday efficiently and effectively.
In spite of my doubts, I went ahead with my study, recruiting people who were normal weight and overweight (not obese). My goals for the study were broad: to find out if anyone could actually stay on the diet for a few months, and if they would lose weight. Much to my surprise, they did both!
There were 32 people in the original study.3 Sixteen went on the Every-Other-Day Diet. The other 16 were the control group—they didn’t diet or change their eating habits at all. After three months, my colleagues and I compared the two groups. Not surprisingly, people in the control group didn’t lose any weight. But all of the every-other-day dieters shed pounds.
The folks who were normal weight at the start of the diet lost an average of 11.9 pounds after three months. Those who were overweight lost an average of 11 pounds. (A few of them lost as much as 25 pounds.) The overweight group also saw significant drops in bad cholesterol (low-density lipoprotein, or LDL) and in high blood pressure. And most of the participants said they didn’t find the diet difficult at all.
I had proven to myself that every-other-day dieting was a reasonable, effective approach to weight loss. People could eat 500 calories every other day on Diet Days, without difficulty. People could eat whatever they wanted on Feast Day and still lose weight.
As you can imagine, I was very excited about this first set of results. After all, just about everybody hates daily dieting. Don’t you? You hate the endless weeks and months of nonstop deprivation. You hate the constant hunger. You hate the complicated requirements and rules. That’s why you’ve probably quit most of the diets you’ve started. Who wouldn’t? Daily dieting is a drag. But every-other-day dieting is a new and effective way for people to lose weight—without deprivation, without hunger, without rigid rules.
After the success of this first study, there were many other questions about every-other-day dieting that I wanted to answer, with detailed, careful, and repeated research:
Nearly a decade later, after six more studies on people and more than 20 published scientific papers on every-other-day dieting, I’m proud and delighted to say that these questions have been answered. In fact, it’s only because they were answered that I feel comfortable presenting the Every-Other-Day Diet to the tens of millions of people who really want to lose weight and keep it off and not just be disappointed by another every-day diet.
Let’s take a closer look at a few of my studies and what I discovered. To make it easier for you to follow the trail of my research, I’ve listed the year each study was published, the journal it was published in, and the specific findings of the study.
A study in the American Journal of Clinical Nutrition was the first to definitively show that every-other-day dieting works to help obese people lose weight.4
My colleagues and I studied 16 obese people, 12 women and 4 men, with an average weight of 213.4 pounds and an average BMI of 33.8. All of them went on the diet for two months. For the first month, they ate frozen and other packaged foods for their 400-to 500-calorie lunches and 100-calorie snacks on Diet Day. (We distributed the lunches and snacks on a weekly basis.) For the second month, they prepared the Diet Day lunches and snacks themselves, after meeting with a nutritionist on our staff who counseled them about the calorie level of Diet Day and the foods and portion sizes that would help them stay at that level. (You’ll find all the practical details for Diet Day in chapter 2.)
The results:
An average of 12 pounds of weight loss. After two months, the average weight loss was 12.3 pounds, a steady, healthy weight loss of 1.5 pounds per week. And the rate of weight loss was just about the same whether the participants were given frozen and packaged food or they prepared their own food. They just kept losing pounds, week after week.
Dieters lost fat, not muscle. Our EOD dieters also lost most of their weight as fat—11.9 pounds, on average, meaning that they shed only a few ounces of muscle. Losing fat rather than muscle is crucial in successful weight loss, because muscle burns calories. A typical dieter on other plans sheds 75% of her weight as fat and 25% as muscle; the typical EOD dieter sheds nearly all of her weight as fat. That’s probably one reason why my subsequent studies have shown that EOD dieters, unlike most other dieters, don’t regain the weight they lose.
Their BMI fell. The average BMI also dropped to 29.9. Many people who were classified as obese at the start of the study were now classified as overweight. That’s a significant and health-giving improvement: as BMI decreases from obese to overweight, so does a person’s risk for many diseases, including heart disease (obesity doubles risk), diabetes, arthritis, and cancer.
There was very little cheating. Our records showed that, on average, the dieters managed to meet the 500-calorie requirement of Diet Day for about 9 out of 10 Diet Days throughout the two months of the study. This showed me that the Every-Other-Day Diet is a diet people could and would follow at home.
Cholesterol plummeted. We also saw big decreases in total cholesterol (21 points) and LDL cholesterol (25 points), decreases that lower the risk for heart attack and stroke.
Dieters had lower blood pressure. Systolic blood pressure (the upper number of the blood pressure reading, reflecting arterial pressure when the heart pumps blood) dropped, on average from 124 to 116. Lower blood pressure means a lower risk for heart attack or stroke.
Dieters had a slower heart rate and a stronger heart. The participants also saw a startling drop in average heart rate, from 78 beats per minute to 74—a sure sign of a stronger, healthier heart.
My scientific conclusion: The Every-Other-Day Diet is an “effective diet strategy to help obese individuals lose weight and to confer protection against coronary artery disease.” That’s what I wrote (in the formal, restrained language of scientific discourse) in the American Journal of Clinical Nutrition.
For this book, I’ll also state my conclusions about my studies a little more personally and enthusiastically: the Every-Other-Day Diet works—and it’s really good for you, too!
Now I knew that every-other-day dieting worked for obese people. But I wanted to know more details about the diet:
To learn the answers to these questions, I analyzed some of the data from my first study more closely. I discovered the following:
There was no overeating on Feast Day. I thought the obese participants in my study would eat a lot more on Feast Day to make up for the caloric restriction of Diet Day, but they didn’t. On average, the dieters ate the same number of calories they always ate (and even a little less), consuming an average of 95% of their normal caloric intake on Feast Day. In other words, Diet Day was not followed by Overdo-It Day!
Hunger vanished. My colleagues and I asked the study participants to rate their hunger on the evening of each Diet Day, using a scale of 0 to 100; 0 was “not at all” hungry, and 100 was “extremely” hungry. After three weeks of dieting, the average ranking was 60. After four weeks, it was 50. And after seven weeks it was 35. In fact, after about two weeks on the Every-Other-Day Diet, most of the participants said they felt little or even no hunger on Diet Day. That’s more good news, because it’s constant, gnawing hunger that drives most people to cheat on or quit a diet.
Satisfaction with the diet increased week by week. Meanwhile, over the eight weeks of the study, satisfaction with the Every-Other-Day Diet went up and up. Using the same 0 to 100 scale, the study participants reported a satisfaction level of 35 in the first weeks of the diet, but a satisfaction level of 50 by week eight. In other words, their good feelings about being on the diet—and no doubt their pride in the results as pounds kept peeling off—increased week by week. I’m pretty sure you’ll have the same experience.
Physical activity wasn’t a problem, even on Diet Day. We measured the level of physical activity throughout the study by asking the participants to wear a pedometer, a device that measures the number of steps taken every day. Two thousands steps is about one mile, and most of us take between 4,000 and 7,000 steps a day.
I thought the study participants would feel less energetic on Diet Day and would take fewer steps. But that wasn’t the case. The average number of steps on Diet Day and Feast Day were almost the same: 6,416 on Diet Day, and 6,569 on Feast Day. This was more good news: The Every-Other-Day Diet doesn’t slow you down!
My scientific conclusions: “These preliminary data offer promise for the implementation of alternate-day fasting as a long-term weight-loss strategy in obese populations,” I wrote in Nutrition Journal. I had made many additional discoveries about the Every-Other-Day Diet:
My next and very important question: Could this diet help prevent and reverse heart disease? The answer, as you’ll read in a moment, was an unqualified yes.
In my first study, the participants not only lost weight; they gained health.6 Specifically, they gained added protection against heart disease:
A 21% decrease in total cholesterol. Their total cholesterol dropped from 175 to 138 mg/dL, for an average decrease of 21%. Every 1% drop in total cholesterol lowers the risk of heart disease by 2%, which means the Every-Other-Day Diet lowered the risk of heart disease by a whopping 42%. Not a bad “side effect” of successful dieting!
A 20-point drop in LDL cholesterol. LDL is the type of cholesterol that can build up on an artery wall and clog the artery, causing a heart attack or stroke. After eight weeks, the study participants had an average drop in LDL from 102 mg/dL to 72 mg/dL. This took them right to the 70 mg/dL level that doctors try to achieve in patients at risk for heart disease by prescribing a cholesterol-lowering statin like Lipitor or Zocor. (Personally, I’d rather lose weight than take a statin, since these commonly prescribed drugs are linked to fatigue, muscle pain, memory loss, and other health problems.)
Triglycerides fell from 125 mg/dL to 88 mg/dL. Like cholesterol, triglycerides are a blood fat that can raise your risk of heart disease. The study participants went from the “normal” to the “optimal” level of triglycerides, as defined by the US government’s National Cholesterol Education Program.
Systolic blood pressure fell from 124 to 116 mm Hg. Eight points might not seem like much of a decrease, but it meant the difference between some of the study participants being prehypertensive—just below the level where a person would be diagnosed with outright high blood pressure—and having a normal blood pressure level, below 120.
My scientific conclusion: “Alternate-day modified fasting may decrease the risk of coronary heart disease in obese individuals,” I wrote in Obesity, the world’s leading scientific journal on the topic, in 2010. Given that heart disease kills 600,000 Americans every year, that’s a very important finding.
In my first two studies on every-other-day dieting, participants ate low-fat foods on Diet Day—because low-fat foods like fruits, vegetables, whole grains, and beans provide more filling bulk for fewer calories. But most Americans don’t eat a low-fat diet. Just the opposite. They eat a high-fat diet, with 35% to 45% of calories from fat.
Since I wanted the Every-Other-Day Diet to work for everyone, I needed to find out if it could work for people who eat a high-fat diet on Diet Day while still maintaining the 500-calorie limit. To that end, I conducted a study with 32 obese people, putting them on the Every-Other-Day Diet for eight weeks. On Diet Day, 16 people ate high-fat foods that delivered 45% of calories from fat. The other 16 ate low-fat foods, with 25% of calories from fat. We prepared the foods for both groups, to guarantee their fat content.
The results:
The folks eating high-fat foods on Diet Day lost MORE weight than those eating a low-fat diet! That’s right: after eight weeks on the diet, those eating high-fat foods had lost more weight than those eating low-fat food—9.5 pounds, compared to 8.2 pounds.
They had trimmer tummies. Both low- and high-fat groups trimmed nearly 3 inches off their waistlines. Dietary fat didn’t make anybody fatter.
They had healthier hearts. Both groups had healthy decreases in total cholesterol, LDL cholesterol, and triglycerides.
My scientific conclusion: “An alternate-day fasting/high-fat diet is equally effective as an alternate-day fasting/low-fat diet in helping obese subjects lose weight and improve coronary heart disease risk factors,” I wrote in the journal Metabolism.
Why did the people eating a high-fat diet lose more weight? Well, they were slightly less likely to go off the diet on Diet Day, cheating 13% of the time, compared to 22% for the low-fat dieters. And I think it’s likely they stuck to the diet because it was high-fat and therefore more enjoyable and satisfying.
Bottom line: The Every-Other-Day Diet works even if you eat high-fat foods on Diet Day. When it comes to weight loss, it’s not fat that makes the difference. Or carbohydrates. Or protein. It’s calories. Stick to the 500-calorie limit on Diet Day and you will lose weight.
My first studies found that people didn’t become less physically active when they were on the Every-Other-Day Diet, on either Diet Day or Feast Day. A modified fast didn’t modify their capacity to move around. But, I wondered, what would be the effect of combining the Every-Other-Day Diet and exercise—not just daily physical activity, but a regular workout? Would people lose more weight than they would by dieting alone? Would their hearts be even healthier? My next study on the Every-Other-Day Diet attempted to answer those questions, by comparing people who went on the EOD Diet to people who went on the EOD Diet and exercised.
You can read all about this study in chapter 6, “Every-Other-Day Dieting and Exercise,” but here’s the super-positive bottom line: At the end of the study, folks who went on the EOD Diet and exercised had twice as much weight loss, had more muscle, banished more belly fat, lowered LDL cholesterol, and raised HDL cholesterol. The diet-alone group had only lowered LDL cholesterol.
My scientific conclusion: The combination of the Every-Other-Day Diet and exercise “produces superior changes in body weight, body composition [muscle and fat], and lipid [blood fat] indicators of heart disease risk, when compared to individual treatments,” I wrote in Obesity.
Or, to put it less scientifically and more plainly: if you want the best results, go on the Every-Other-Day Diet and exercise.
As I’ve pointed out several times in this chapter, the sad fact of weight loss is that it’s almost never permanent. In a study published in the International Journal of Obesity, only 3% of people studied maintained their weight loss after five years. Other studies are a little more positive (but not much); they estimate that 80% to 90% of dieters regain all their weight.9
Unfortunately, most diet books ignore this fact. Or they make an enthusiastic but baseless pronouncement about how you’ll maintain your weight after the diet. They might as well be telling you to believe in Santa Claus. I think any diet book that doesn’t give you a science-proven, evidence-based program to maintain yourself at the weight you reached on the diet—and that’s just about every diet book out there, including most of the other diet books on intermittent fasting—is setting you up for disappointment, not to mention the health problems that can go with regaining the weight you’ve lost. The Every-Other-Day Diet isn’t that kind of diet book. It includes the Every-Other-Day Success Program, which you’ll read about at length in chapter 7.
In November 2013, several months after completing the writing of this book, and six weeks before its publication, I reported the preliminary results of that study at the annual “ObesityWeek” conference, the world’s most prestigious conference on obesity and weight loss.
Dieters had only 1 pound of regained weight. In the first six months of the study, people were on the Every-Other-Day Diet, and many people lost a lot of weight (up to 45 pounds). In the next six months, the folks who were on the EOD Diet went on the EOD Success Program. My preliminary results showed that they regained an average of 1 pound. Meanwhile, the control group—people who went on a standard, every-day, calorie-restricted diet for six months and then went off the diet—regained an average of 5 pounds.
I’m also happy to say that all the heart-healthy benefits of the Every-Other-Day Diet—lower LDL cholesterol, lower triglycerides, and less belly fat—were maintained during the EOD Success Program. The participants also had lower levels of blood sugar and insulin, a sign that they were less prone to developing type 2 diabetes.
It’s been a long journey from that basement at Berkeley to a three-year, multimillion-dollar study sponsored by the National Institutes of Health; from the lightbulb of having a fresh idea to the light at the end of the tunnel for millions of people who have failed to lose weight on other diets, or who have shed pounds only to see their weight return.
My comprehensive research shows that the Every-Other-Day Diet is a wholly unique and effective way to lose weight and keep it off without daily deprivation, without hunger, and without complex and hard-to-follow rules. My research also shows the diet can help prevent and reverse several risk factors for cardiovascular disease, the #1 killer of Americans. And with all this positive research under my belt, I am very comfortable making you a promise about the weight you will lose on the EOD Diet.
I’m sure you have one big question at this point: Just how much weight can I lose on the Every-Other-Day Diet? Well, I am happy to report that you can lose:
12 pounds per month. In my most recent research, many EOD dieters lost up to 12 pounds in the first four weeks of dieting, or 3 pounds per week—the promise on the cover of this book.
Up to 50 pounds. In my two- and six-month studies, some EOD dieters lost up to 50 pounds.
Of course, there’s no guarantee you’ll lose weight on the EOD Diet. In my studies, the rate of weight loss depended on how heavy my participants were when they started (the heavier you are, the more you lose); their level of motivation; and even the time of year when the study was conducted (it’s harder to lose over the holidays). But if you eat 500 calories on Diet Day and whatever you want on Feast Day and stick to that pattern, it’s nearly a certainty that you will lose weight at a steady rate, until you reach your weight-loss goal, whether that’s losing 10, 25, 50, or 100 pounds or more.
And when you have reached your goal, it’s time to implement the Every-Other-Day Success Program, the lifetime approach to keeping off the weight you just lost. You’ll find the practical details of the Success Program in chapter 7. So what are you waiting for? Let’s get started!