5
Your Life, Your Decision
We are constantly amazed at how many people we speak with get hung up on the question of whether the Longevity Diet “really works,” given the lack of any present evidence of regimen-followers living a record-breaking number of years. True, we won’t know with absolute certainty until after the year 2100 or so whether the Longevity Diet in humans genuinely slows the aging process itself as has been projected, if the studies that have recently commenced even continue that long. But while the gold standard of antiaging studies—which is to say, animals (human or otherwise) living past the age of the longest known member of his or her species—can’t be achieved for another century or so, there is nonetheless overwhelming evidence that such a diet will indeed slow the aging process, and the facts are even more solid when it comes to the effect of the Longevity Diet on diseases associated with aging, such as type 2 diabetes and heart disease.
Imagine that no long-term, controlled study had ever been done specifically on the relation between smoking and health in humans. Imagine that we “only” have hundreds of studies showing that smoking shortens the lives of a wide variety of lab animals; that we have short-term studies in humans showing that smoking increases plaque formation in blood vessels, damages tissue in the mouth, throat, and lungs, damages skin on the face, and in many other ways appears to be extremely deleterious to your health. In addition, imagine that we also have many theories about how smoking shortens the life of the animals in the lab studies: about the effects of carbon monoxide in their blood, and of the high temperature of the smoke upon their oral passages and respiratory system, and of tar in their lungs; and so on. Now imagine that we can actually measure increased carbon monoxide in humans who smoke, the effects of the high-temperature smoke on the tissue in their mouths and throats, the presence of tar and other chemicals in their lung tissue, etc. And that not only do we see the lab animals that are exposed to smoke over the course of a lifetime often coughing up disgusting black stuff from their lungs shortly before they are going to die; we see humans who smoke for many years coughing up disgusting black stuff from their lungs. Would it make sense to say, “Gee, I don’t know whether I’m going to quit smoking. I need to wait until the long-term, carefully controlled studies with humans are completed.” Of course it would not make sense! When it comes to your health, waiting for 99.5 percent certainty to go up to 99.9 percent would be silly.
But it would not be silly in the slightest to say that you don’t want to quit smoking because you love smoking. That’s an entirely different matter! Same thing with deciding that you don’t want to give up your current eating habits.
You may decide you just don’t want to change the way you eat. The pleasure of dining on rich, fatty foods, the intense pleasure of excess, is delightful, and may quite simply be something you do not want to give up. We’re not on any kind of moralistic crusade against obesity. Indeed, there’s far too much moralizing about food and weight as it is—food guilt has in and of itself become a huge problem in our society. We should not make people feel bad because of the way they choose to eat (and certainly not because of the way they look).
You should feel good about yourself, about whatever decisions you make in life. But if you have decided that living a long, youthful life is important to you, try the Longevity Diet!
Our only caveats: if you are pregnant or trying to become pregnant, are not yet fully grown, have a history of eating disorders, or have not been to a health-care professional about beginning this diet, do not proceed with the diet. But, even if you fit one of these special situations, please keep reading, as we still have much to say concerning basic nutrition and health.
If you are pregnant, or even thinking about getting pregnant, don’t try the Longevity Diet.
CR during pregnancy has not been studied extensively. Either way, CR during pregnancy is a risk—to mother and child—not worth taking. Given what we know about the evolutionary role of the CR effect, it would make sense that the Longevity Diet could also make it more difficult to get pregnant.
If you are not fully grown, don’t try the Longevity Diet.
When begun before the animals have physically matured, severe CR stunts the growth of laboratory animals. Don’t try the Longevity Diet if you’re not fully grown!
If you have a history of eating disorders, we would suggest avoiding the Longevity Diet.
People with eating disorders, or those who have had an eating disorder, are severely at risk of slipping into another episode if they attempt this diet, because they have a predisposition toward an unhealthy body image and/or unhealthy obsessions about food. If you have or have had an eating disorder, you should not eat fewer calories than have been prescribed by your doctor.
If you haven’t spoken with a health-care professional, don’t try the Longevity Diet—indeed, don’t try any diet!
Talk with your doctor before making any significant changes to your diet. Always! We should all have good, long-term relationships with our physicians. Your doctor knows you, your medical needs, your habits, and so on.
If you want to start the Longevity Diet, and your doctor agrees it’s a good idea, you will probably have a lot of questions about precisely how to put its principles into practice. Part 2 of this book will explain the various forms of the regimen.
Before we turn to part 2, however, there are still a few remaining technical matters that we need to address.

How Much to Reduce Your Intake of Calories

The concept of the Longevity Diet is simple: Reduce your caloric intake, while being certain not to fall short on essential vitamins and other nutrients, and your health will be greatly improved, and your body will almost certainly age more slowly.
But reduce from what level, and to what level? The question of your optimal CR energy intake is one of the trickiest in the application of CR to humans. There is at least as much art as science here. We will offer three different approaches: (1) “weight watching,” (2) calorie counting, and (3) measuring health markers (which should to some degree be a part of any attempt to improve health).
Key to determining how much to restrict your energy intake is the notion of set point. Set point is, technically speaking, difficult to define, yet intuitively it makes a lot of sense: it is how much your body “wants” to weigh, the weight your body tends toward if you make no special effort to lose or gain weight. We all have met people who find it extremely difficult to lose weight. Even if they are moderately active, and if they eat what and when their body tells them to, and not more, they end up very heavy. Their body still seems to “defend” a higher weight than other bodies do. And then there are those extremely scrawny people who have to “remember to eat” to not become even scrawnier. The first kind of person is one with a high set point; the other, with a low set point.
Laboratory animals, of course, also have set points. One species of mouse known as the “ob/ob” mouse (yes, “ob” stands for obesity, and this mouse has two copies of this particular obesity gene) has an extraordinarily high set point. An ob/ob mouse is so fat it almost looks like a “mouse puddle”—a flattened, circular, fluid blob with a tail on one end and little ears and eyes on the other. These mice have really bad genes! On a very severe CR regimen, begun early in life, these mice still do not end up particularly scrawny, yet they live 40 to 50 percent longer on this regimen. They can’t be taken to much more extreme levels of CR without endangering their health, even though they are not at all emaciated.
Remember, CR is not about trying to be thin. Weight loss is of course a side effect, but it is not the goal. The goal is putting your body into a state where its energy economy is altered such that maintenance and repair are prioritized. This state is achieved when the body is given less energy than it normally “wants,” which will result in the body weighing less than it normally would “want” to weigh.
Technically, set point is often defined as what you weighed during relatively normal periods of your life in your mid to late twenties. If you were training for a marathon when you were twenty-seven, ignore what you weighed then. If you had to gain fifty pounds to play the part of Henry VIII in your local community theater when you were twenty-nine, ignore what you weighed during that time. Just think of what your “normal weight” was during your early adult years. That’s your set point, at least as it is often defined by scientists.
Where the art of set point comes in, is that many of us have to make some adjustments to that scientific definition. If you were always training for a marathon in your mid to late twenties, and, especially, if you are significantly thinner than everyone in your family, your set point is probably higher than what you weighed during that period. Your body probably “wanted” to weigh more, to receive more calories, than it did during that period, but wasn’t able to because of your training program. And, of course, you may be above your set point for cultural, subcultural, or psychological reasons. Set point, in so far as it is genetically determined, is not likely to have changed in the course of one or two generations. Yet in the United States, and increasingly, many other countries, average weight has gone way, way up. Determining whether or not your typical weight during your young adult years was the result of your genetic program or cultural influences can thus sometimes be a tricky matter. But once you’ve got a good idea what your set point is, you’ll be ready to start determining your Longevity Diet target weight.

The “Weight Watcher” Strategy

With the “weight watcher” strategy, you will plan to lower your body weight by 10 to 25 percent, slowly, over the course of many months, if not a year or two. Early studies of extreme CR initiated in adulthood in laboratory animals did not lengthen life, and in some cases even shortened it.1 The adult body needs time to adjust, at least for more extreme versions of CR. We will explain more about the “caloric descent” in part 2.
If your set point is relatively high, you can probably aim for a 25 percent reduction in weight, perhaps even more, if you’re very overweight to begin with. If your set point is very low, reducing your body weight by more than 10 percent could be risky, since there are health problems sometimes associated with extremely low body weight (more specifically, with a BMI below 14 or 15). Remember, of course, to talk with your health-care professional about any significant decisions you make about your health and to get a few basic tests of the state of your health done before changing your diet. Tests of your health, along with a basic checkup from your doctor make questions of set point and percentage weight loss less important, especially if your goal is primarily simply to improve your health, as opposed to trying to live to be 120 or 130. See sidebar below for some tests you should take. Some of these, such as blood pressure and cholesterol levels, are very likely familiar to you. Others might seem a bit obscure, but your doctor can explain them to you.
Tests you can easily do at home
Body weight (taken under same conditions each day; upon waking is best). Your weight will of course decrease on CR.
Resting pulse (taken the same time each day, under the same conditions, preferably upon waking). Your resting pulse will almost certainly decrease on CR. Most people on long-term CR have resting pulses between 40 and 60.
Body temperature (and save the thermometer, in case it is calibrated incorrectly). Your body temperature should decrease on CR. Most people on CR have a body temperature 1 to 2 degrees Fahrenheit below their pre-CR body temperature.
Relatively simple, generally cheap tests your health-care professional can order for you
Fasting glucose. Your fasting glucose levels should decrease significantly on CR. Most people on CR have a fasting glucose level between 70 and 85 mg/dl.
Lipids panel (includes total cholesterol, HDL, LDL, and triglycerides). On CR, total cholesterol, LDL, and triglycerides should decrease. HDL should increase.
Blood pressure (ask for this at every doctor’s appointment; also, ask for weight and temperature, for comparison with your own measurements). Both systolic and diastolic readings should decrease on CR. Most people on long-term CR have blood pressure between 95/55 and 110/70.
Slightly more expensive (listed roughly in order of importance)
• T3. T3 should decrease on CR. Most people on CR have values between 55 and 90 ng/dl.
Fasting insulin. Fasting insulin decreases on CR. Fasting insulin is usually between 0.8 and 2.0 mlU/ml in long-term CR practitioners.

The Calorie Counter Strategy

Another approach is to focus more on how many calories you currently eat, instead of your weight. If you or your doctor thinks you may be overweight, then pick a reasonable target for reduction in calories. If you are in your fifties or sixties or older, reducing energy intake by more than 20 to 30 percent for the long haul is about as far as you should go, unless you’re very overweight. But start slow! If you’re forty, and currently eat around 3,000 calories /day, and if you simply replace high energy-dense foods with low energy-dense foods, you’ll very likely naturally eat less than 3,000 calories/day, without making any conscious effort to eat less. And you’ll lose weight. If you track what you eat, you’ll probably see you’re eating 2,500 or 2,600 calories/day. Stay at that level for a few months. Enjoy your new way of eating. Then check with your doctor, discuss your plan to go down to 2,300 or 2,400 calories /day, get a few simple tests of your health done, and proceed. If you feel good, aren’t too hungry, and want to get even more CR benefits, check in again with your doctor after a few more months, get a few tests done, and discuss your plan to go further on your caloric descent, shooting maybe for 2,000 calories/day. As long as your health is being tracked by a doctor, and remains strong (and it will probably improve greatly), reducing your caloric intake to 2,000 will almost certainly improve your health further, and poses no risks.

The Health Marker Strategy

Some people have the time and money to get lots of tests done very frequently—once every two or three months. One of our friends on CR puts it this way:
I don’t really know what my set point is. I’m a 5’10”, 37-year-old man who weighed around 170 pounds in my twenties, I have a somewhat thick bone structure, so I wasn’t at all overweight at 170 pounds, I just had some “love handles.” Two years ago when I decided to try the Longevity Diet I more or less guessed that ending up at 145-150 pounds would be a good “CR level” for me. I’m not even sure what reduction in calories that translates to. But I didn’t care. I got my cholesterol levels and fasting glucose levels tested (both of which were not so great), and focused first on eating more healthy foods. It wasn’t really consciously following CR or the Longevity Diet, I was just eating more “health food.” I naturally lost eight pounds very quickly. Then I got more tests done after around two months, and saw that my health had improved. I stuck with that approach for another few months, then started consciously eating less. I still wasn’t counting calories, but I weighed myself a few times a week.
I started to read food labels to make sure I was getting enough protein. I knew I was getting enough vitamin A and
C because of all the veggies and fruit I was eating. Same thing with essential fatty acids. And I was almost certainly getting enough B vitamins, but I took a multivitamin pill just to be safe. After a while I had to have a few simple rules to keep my weight from going above 150, such as not eating after 9:00 p.m., and not snacking between lunch and dinner.
It was hard at first, but I kept thinking about the lowered glucose levels in my blood, the lowered levels of free radical damage, DNA damage, etc. It made it fairly easy to think of the last few hours of the evening as nonsnacking hours. They were my “hours of freedom from free radicals.” And I pop in to my doctor’s to get tests done every 2-3 months.
He says my health is excellent, so, even though I’m being kind of “loose” about my CR, it seems to be working extremely well. I may drop down a few more pounds, but I’m going to wait another year or so, just to make sure my current plan “sticks.”

The Elderly and CR

Older souls may be wise and strong, but older bodies tend to be wizened and weakened. We know from animal studies that older animals often don’t adapt well to extreme reductions in energy intake. There is of course evidence that those who are over sixty and obese will live longer if they lose weight, but if you’re over sixty and not grossly overweight, you should be especially cautious with your Longevity Diet program. You have a huge amount to gain, maybe many extra decades, but don’t risk that gain by rushing headlong into an extreme dietary change. Readers over sixty or so (this is a somewhat arbitrary cutoff point, since the relevant studies have not yet been done) should discuss this program thoroughly with their health-care professional, and proceed slowly.