For the vast majority of dieters “calorie restriction” simply means reducing the number of calories they normally eat in order to lose weight, but for scientists investigating the potential benefits of restricting one’s daily intake, that means allowing approximately 60 or 70 percent of what would be considered the “normal” caloric requirement to maintain weight while also maintaining optimal nutrition.
Probably the best-known and primary proponent of what its followers call Calorie Restriction with Optimal Nutrition, or CRON, was Roy Walford, mentioned in the introduction, who studied the phenomenon for many years at UCLA and produced significant evidence to support the theory that CRON could potentially extend human life to an average of 120 years.
PROOF THAT THIN IS BETTER
In 1935, Clive McCay, a well-known professor of nutrition at Cornell University, showed that rats fed a calorie-restricted diet lived longer, had less disease, had litters at later ages, and were much more active than the freely fed rats.
More recently, researchers have shown that restricting calories in lower life forms—including yeast, roundworms, and fruit flies—significantly prolonged their lives. In fact, Calorie Restriction, or CR, has been shown to prolong lifespan by amounts ranging up to 80 percent in virtually every species tested. Most important for humans, our close relative the rhesus monkey has been studied for more than fifteen years, and in every study the monkeys subjected to calorie restriction have appeared to be healthier than the freely fed controls.
Taking these studies a step further, Walford observed that by feeding rodents approximately 30 to 40 percent less than they would normally eat, they lost 10 to 25 percent of their normal body weight and lived 30 to 40 percent longer than their normal lifespan (that is, the lifespan of the normally fed control group). Although he was not specific about exactly how many calories any given individual should consume in a day, he did state that one ought to aim for a weight that is 10 to 25 percent below what was one’s set point—the weight to which one’s body naturally gravitates—during one’s teenage years (assuming one was neither anorexic nor obese as a teenager) in order to achieve maximum metabolic efficiency and longevity. Weight loss, however, was considered incidental to the true goal of the diet, which was, first and foremost, to maximize health and longevity. And according to Walford, simply increasing one’s activity level to burn additional calories, even if it resulted in weight loss, would not have the same health benefits as calorie restriction. (In fact, it is virtually impossible to increase one’s activity level enough to achieve and maintain the degree of weight loss he recommends.) In truth, exercise alone, without calorie restriction, doesn’t work for weight loss in general. It does, however, have other, important health-enhancing benefits, as you’ll be learning in Chapter 6.
While most of Walford’s testing was done on laboratory animals (as well as on himself), he had the unique opportunity to investigate the benefits of CRON on a group of human test subjects when he and seven fellow scientists entered Biosphere 2 in 1991 and discovered that their enclosed, self-sustaining environment was incapable of producing as much food as had been anticipated and would, therefore, be unable to supply the number of calories they were currently consuming. Although there was some initial discussion of simply abandoning Biosphere 2 altogether, Dr. Walford was able to persuade his fellow researchers that following a CRON diet for two years wouldn’t harm them—and, in fact, could well improve their health and extend their life.
Since the group was dependent upon whatever food they could produce, their diet was consequently nutrient-dense—no calorie-dense and nutrient-deficient McDonald’s or Dunkin’ Donuts available. When the eight emerged after two years, they had all lost significant amounts of weight—the men on average about 18 percent and the women 10 percent of their pre-Biosphere body weight. They were all “thinner-than-thin,” but there was no evidence that they were malnourished. Rather, tests indicated that they were actually nutritionally healthier than when they had gone in: Their cholesterol, triglyceride, fasting blood sugar, insulin, and blood pressure levels had all decreased. In fact, every one of the regularly measured laboratory markers showed results that were consistent with Dr. Walford’s rodent studies in terms of their percentage of youthful values.
Calorie-dense foods contain a high number of calories per unit of volume, meaning that you get a lot of calories for very little food. Nutrient-dense foods contain high levels of minerals, vitamins, phytonutrients, and other unknown factors that contribute to good health. Generally speaking, calorie-dense foods are nutrient-poor. (You may have heard them called “empty calories.”) Nutrient-dense foods are usually lower in calories.
Humans have been genetically programmed to prefer foods that are high in fat and sugar, which are calorie-dense and not usually natural. Our obesity problem originates with our natural desire to consume these foods. The more readily they are available, the more we eat.
The opposite of calorie-dense foods are those with low calorie density. These are the foods on which many diets have been based. Among the most notable recent entries in the category of low-calorie-density diets is that recommended by Barbara Rolls in her book Volumetrics. The theory is that by eating a largely plant-based diet with a high water content, you will be able to eat more food while consuming fewer calories and will, therefore, feel full. One study done at Pennsylvania State University showed that dieters who ate a cup of soup or a salad before their meal consumed fewer total calories. Broth, fruits with high water content, nonstarchy vegetables, and lean proteins are part of this plan. In the Alternate-Day Diet the choice of foods recommended for both the “down days” and the “up days” is nutrient-dense and low-calorie.
The evidence appears to be clear: According to Walter Willett, chairman of the Department of Nutrition at the Harvard School of Public Health, and a leading nutritional epidemiologist, the thinner we are, the healthier and longer-lived we will be. In the revised edition of his excellent book Eat, Drink, and Be Healthy, he states, “The lower and more stable your weight, the lower your chances of having or dying from a heart attack, stroke, or other type of cardiovascular disease; of developing high blood pressure, high cholesterol, or diabetes; of being diagnosed with postmenopausal breast cancer, cancer of the endometrium, colon, or kidney; or of being afflicted with some other chronic condition.” And he goes on: “Keeping that number [your weight] in the healthy range is more important for long-term health than the types and the amounts of antioxidants in your food or the exact ratio of fats to carbohydrates.” For example, being overweight doubles or triples your likelihood of heart disease. Even the effect of eating eight or more servings of fruits and vegetables a day compared with eating only 1.5 servings per day decreases the incidence of heart disease by only 25 percent and doesn’t affect the overall incidence of cancer. Obesity and physical inactivity, on the other hand, may account for up to 30 percent of several major cancers including colon, endometrial, kidney, postmenopausal breast cancer, and cancer of the esophagus.
Although there are some studies that seem to indicate that being somewhat overweight is healthier than being very thin, life insurance companies—whose job it is to, in effect, bet on how long any given individual is likely to live—have used data collected over many years to conclude that death rates increase in people whose body mass index (BMI), a number that represents the relationship of height to weight, is higher than 21.
The primary source for these claims comes from studies in which groups of healthy people were followed for a period of approximately ten years. Their death rate was then examined in relation to their BMI. The studies showed that the number of deaths increased as BMI increased, meaning that the fatter you are, the more likely you are to die sooner.
Your BMI is calculated by dividing your weight in pounds by your height in inches squared and then multiplying that number by 703.
Many people who understand that Calorie Restriction prolongs lifespan say they don’t want to simply “hang on” and experience the decrepitude of old age. But the good news is that studies indicate that older people who are in good health, as indicated by certain markers of aging, don’t just live longer, they also have a longer healthspan—that is, the length of time they are actively mobile with good hearing, eyesight, and cognitive abilities.
In 2004, Luigi Fontana and his colleagues at Washington University in St. Louis published the first in a series of studies they did on members of the Calorie Restriction Society, proponents of restricting caloric intake to around 90 percent of recommended levels for weight maintenance. Their findings indicated that these people had lower risk factors for atherosclerosis, and the elasticity of their hearts was greater than those of the age- and gender-matched control group who ate a standard American diet. The average BMI of the control group was 26. In other words, those with the lower BMI had hearts that were functioning like the hearts of much younger people.
Walter Willett states, “Your body weight is more important than the precise balance of healthy and unhealthy fats or whole grains versus refined carbohydrates or the number of servings of vegetables you eat.”
In two major studies of the relationship between fruit and vegetable consumption and major chronic heart disease, stroke, cancer, and diabetes, the incidence of heart disease was 25 percent lower among those people who ate five or more servings compared with those who ate fewer than 1.5 servings. There was no significant overall reduction in cancer risk. In contrast, for a woman, having a BMI of 30 (the definition of obesity, 180 pounds for a 5’5” woman) is associated with a nearly 50 percent higher likelihood of dying and three times the incidence of heart disease than having a BMI of 21.
While I’m not advocating bad eating—in fact, it’s just the opposite—it is important to understand that body weight supersedes other risk factors. Following the Alternate-Day Diet will minimize the impact of bad food for two reasons: First, because you will weigh less, and second, because it will activate a critical stress response you’ll be learning about in Chapter 5.
Interestingly the Calorie Restriction Society members studied by Fontana et al. had an average BMI of 19.7. If 21 is the optimal BMI according to the life insurance data collected by the Metropolitan Life Insurance Company, these CRON practitioners reduced their BMI by only 7 to 9 percent and yet they demonstrated marked health benefits! And, interestingly, none of the study participants in either group engaged in regular exercise. This and a host of other studies confirm the scientifically accepted wisdom that body weight is the most important factor in long-term survival. Exercise, dietary composition, serum cholesterol, and other risk factors are all of secondary importance.
Despite an abundance of compelling scientific evidence to support a healthier lifestyle, however, Americans are getting fatter. The National Center for Health Statistics reports that from 1962 to 2000 the number of obese Americans grew from 13 percent to 31 percent of the population. Furthermore, an article written by scientists at the Centers for Disease Control and published in the Journal of the American Medical Association indicated that in 2004 obesity was responsible for almost 112,000 deaths in the United States and probably more.
WHY CALORIE RESTRICTION ISN’T THE ANSWER
The health benefits of Calorie Restriction are irrefutable, but CRON is not a way of life that most people can embrace.
In early 2007 journalist Emily Yoffe interviewed Roy Walford’s daughter, Lisa, now a leading proponent of CRON, for an article in the online publication Slate. Ms. Walford reported that she has a BMI of about 15. To get some perspective on what that means, Yoffe writes, “Spanish authorities banned from the runway models with BMIs of less than 18.” Walford is about 5 feet tall and weighs 80 pounds. The article states that in her own book, coauthored with Brian Delaney, The Longevity Diet, she indicated that her usual breakfast consists of four walnuts, six almonds, and ten peanuts.
Lisa Walford has practiced Calorie Restriction for many years. An active, athletic yoga teacher, she has excellent HDL, total cholesterol, and triglyceride levels. In fact, by all indications she will live a long life. Although some very strong-willed individuals are able to achieve these goals, many, if not most, will fall by the wayside.
Aside from the question of whether most people would really want to have a BMI lower than that of most runway models, there is the issue of whether most people would want—much less be able—to spend their presumably increased lifespan consuming exactly twenty specific nuts for breakfast each day. Some critics have even suggested Calorie Restriction is an eating disorder, and somewhat wryly comment that while it may or may not prolong your life, it will certainly seem longer.
Calorie restrictors are exquisitely aware of exactly how many calories they are eating at all times. CRON, in other words, falls prey to one of the biggest stumbling blocks for any diet: It requires you to constantly think about the one thing you don’t want to be thinking about: what you can and can’t eat.
And interestingly, if “April’s CR Diary,” the online journal being kept by one member of the Calorie Restriction Society, is to be taken as typical, CRON followers (or at least a number of the women among them) appear to remain extremely focused on and unhappy with their weight—perhaps because they’re frustrated at not being able to achieve Roy Walford’s “ideal” of maintaining a body weight that’s 10 to 25 percent below the standard optimal BMI of 21.
In the final analysis, however, the major reason why daily Calorie Restriction is not viable for most people is that so few people are able to maintain any level of calorie reduction over time. Surrounded by an increasing abundance of tasty, affordable food, we seem to be unable to restrain ourselves, and, as a result, people are getting fatter. And the problem is by no means limited to the United States. Other developed countries are witnessing similar increases in obesity as they move away from a nutrient-rich to a calorie-dense diet. Even French women do get fat.
The French have long prided themselves on being the thinnest population in the world. But now a parliamentary report states that their rate of obesity is increasing even more quickly than that of Americans and may match it by the year 2020.
While I certainly agree with the cultural and thoughtful approach to food described by Mireille Guiliano in French Women Don’t Get Fat, the reality is that even the French are getting fatter.
The average French family dinner, which lasted 88 minutes twenty-five years ago, now lasts 38 minutes, and the French are becoming more American in their ways of eating in front of the TV, on the telephone, and when by themselves.
Of particular note is that McDonald’s is more profitable in France than anywhere else in Europe. Sales have increased 42 percent over the past five years, and some 1.2 million French, or 2 percent of the population, eat there every day. (By comparison, in the United States, 5 percent of the population eats at McDonald’s on a daily basis.)
In fact the Chinese, the Russians, Eskimos from Greenland, and sub-Saharan Africans are all getting fatter, as is every other population when economic conditions improve and there is increased access to cheaper food. In fact, there are now as many overweight as malnourished people in the world.
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I know myself well enough to understand that daily Calorie Restriction won’t work for me, and if you’ve been battling weight problems, it’s probably not for you either. Like me, however, you may well be able to enjoy the same health benefits by following the Alternate-Day Diet, which is more compatible with—and forgiving of—human nature and allows you to continue enjoying most of the pleasures of eating.