Only a single dietary regimen has ever been conclusively demonstrated to extend lifespan and improve the health of laboratory animals and humans. It is known as calorie restriction. Together with exercise, this is as close to the magic bullet as one can hope for in anti-aging. There are very few, if any, disagreements among anti-aging experts that calorie restriction can increase longevity.
The average human consumes 1,500 calories a day. The average American consumes 2,100 calories a day. For most of the population, calorie restriction means taking in about 20-30 percent fewer calories. For those serious about calorie restriction, the restriction can go up to 40%. In other words, the average-size human on a calorie restriction diet might consume 1,500 calories a day, compared to the 2,100 calories of the typical American. This anti-aging diet is made up of four or five small meals a day and consists predominantly of vegetables and fruits. "It requires a psychological profile only one person in 1,000 has," says Richard Miller, associate director for research at the University of Michigan Geriatrics Center.
Nevertheless, calorie restriction diets are widely practiced by anti-aging experts. The reasons are clear - the list of the beneficial effects of calorie restriction reads like the packaging on a miracle cure. Benefits include: Increased average and maximum lifespans and reduction in occurrence of virtually all age-related diseases, including heart disease, diabetes, autoimmune disease, ocular degeneration, blood pressure, and cancer.These reductions range from two-fold to as much as ten-fold. (For example, 50 percent of female control mice of a particular genetic strain develop breast cancer, but only 5 percent of the same strain developed cancer if on a calorie restriction diet.)
Two caveats - the diets must include plentiful amounts of vitamins and minerals, and the subjects must be undernourished without being malnourished.
Calorie restriction is different from malnutrition, starving or extended fasting. These practices actually accelerate the aging process as they create nutritional deficiencies. Calorie restriction, if properly carried out, provides the body with all the nutrients it needs without overburdening the organs and system functions. By limiting calorie intake to the level required by the body for optimum functioning (as measured by the maintenance of lean body mass), that miraculous machine, your body, will self-regulate. When you eat more food than you need, the engine of your body goes into overdrive in order to digest the food and store what you don't need in the form of fat. If you restrict your food intake to only what you need to maintain a physical and active lifestyle, your body automatically tones down its basal metabolic rate to conserve the limited amount of energy it receives. This is your body's mechanism for survival.
Like an old car, your body's engine needs premium gasoline to prime itself as you age. If you are not mindful of this and continue to abuse your body with "non-premium" gasoline and rough outings (like going on an eating binge), you are causing unnecessary strain to your body's organs. Sooner, rather than later, your body will break down.
What happens to your body as your calorie intake decreases? First, the work necessary to digest food decreases. In other words, there is less oxidative stress. Second, the body's metabolic rate automatically slows and readjusts itself to match your energy expenditure to that of the intake. This is the body's way of preserving itself. Third, the slowing down of your organ system gives your organs more rest and prolongs the lifespan of each of the organs. As your organs remain healthy, you live longer.
Malnutrition and starvation are extreme forms of calorie restriction, which is age accelerating and should be avoided. A car cannot run without gasoline, and your body needs food to generate energy. During malnutrition or starvation, your body breaks down your muscles and organ structures for energy, which is very destructive.
The question of how calorie restriction works is still open to debate. The leading hypothesis is that calorie restriction reduces the amount of oxidative damage to the body. Oxidative damage is the foremost theory as to what causes the deterioration that comes with age. This concept is known in anti-aging as the "oxygen paradox." While oxygen is required for life and cellular fuel, the side effects of oxygen metabolism are detrimental to our health. The process takes place in cellular factories called mitochondria, where energy for our body is produced and by-products called free radicals are also produced. These free radicals are short-lived but voracious agents that oxidize and damage tissues. The oxidation that occurs in the human body is identical to the way in which rust is formed on metal, so it is not unreasonable to say that we will all eventually "rust to death" if given the opportunity. The free radicals not only damage the tissue, but also seem to damage the DNA, genetic material that codes for proteins required for the body's physiological functions.
Calorie restriction reduces the amount of fuel available for cells and the amount of oxygen needed by the mitochondria to convert the existing fuel into energy, and it makes the existing metabolic process more efficient. With calorie restriction, fewer free radicals are generated, the production of enzymes that neutralize the free radicals increases, and growth hormone levels increase.
Calorie restrictions' effect of lowering oxidative damage is targeted at critical cells in organs, such as the brain, heart, nerves, and skeletal muscle cells. All these tissues depend heavily on mitochondrial energy metabolism to generate cellular energy, and all these tissues have fairly limited self-repair ability.
In addition to lowering oxidative damage, calorie restriction has been proven to increase endogenous growth hormone release from the pituitary gland. Raising the growth hormone level is key in deterring the aging process, as symptoms of aging follows the decline in growth hormones in our bodies.
Calorie restriction also stimulates the release of our body's internal antioxidants, such as super oxide dismutase (S.O.D.). Research has shown that administration of S.O.D. leads to a reduction of free radicals and an increase in lifespan.
A properly carried out calorie restriction program will limit the amount of sugar intake by up to 90 percent. Sugar is a negative fountain of youth. It accelerates aging and increases the body's cortisol level. Cortisol is a hormone, but unlike other hormones, it increases with aging. It is sometimes called the "bad" hormone because its increase is linked to accelerated aging.
In summary, calorie restriction:
The demonstration that mean and maximum lifespans are greatly extended in rodents by a calorie restriction diet, was first shown in 1935, by Clive M. McKay at Cornell University. He noticed that the regimen of calorie restriction doubled the lifespan of his lab rats. This observation has been confirmed in dozens of other laboratory test, right up to the present time.
Calorie restrictions' effect on lifespan has been dramatic in every organism thus far tested, from invertebrates (spiders, worms, etc) to fish and rodents. Primate studies are underway, and one may cautiously presume that it may be a "general" effect, and not simply a rodent phenomenon.
In the one closely monitored human study (inside Biosphere 2 for two years from Sept 1991), calorie restriction sharply lowered blood cholesterol (by up to 35 percent), blood sugar and blood insulin (by 15 to 20 percent), blood pressure (20 percent or more), and induced other changes paralleling those seen in calorie restriction rodents and (more recently) monkeys.
The maximum lifespan of humans is about 110 years, and about 39 months for mice. Calorie restriction has extended the 39-month maximum lifespan of mice to an impressive 56 months, which would correspond proportionally to a 158 year-old human. calorie restriction mice stay youthful in appearance, in mental and physical abilities, and show enhanced resistance to disease. These well-established facts are why the calorie restriction diet is now one of the principal areas of research in gerontology, and is receiving major emphasis from the National Institute on Aging.
The National Institute on Aging (NIA), in collaboration with Weindruch and his colleagues, is testing the calorie restriction proposition on rhesus and squirrel monkeys, assuming that if it works for primates, chances are it would work for humans. They now have some 200 monkeys in the trial, half on calorie restriction diet and half eating normally. Even these monkeys are likely to live 30 to 40 years, so the study is a long-term endeavor. But the calorie-restricted monkeys are already showing signs of unnaturally robust health.
Primate studies are currently underway and will help answer the question of calorie restriction and longevity in humans. The studies are ongoing in three different laboratories (University of Maryland, University of Wisconsin, and the National Institute on Aging). It may be 10 more years before we have unequivocal results. (Let us not forget that monkeys live a long time.)
In studies conducted over the past 65 years, calorie restriction works across the whole animal kingdom, so there is no reason to believe that it would not work on humans.
In one interesting and accidental experiment, humans were defaulted to a calorie restriction diet due to a food shortage inside Biosphere 2. It was found quite clearly that these people showed the same physiological and biochemical changes seen in calorie restriction rodents.
Biosphere 2 is a 3.15-acre space in the United States containing an ecosystem that is energetically open (sunlight, electric power, and heat) but materially closed, with air, water, and organic material being recycled. For 2 years from September 1991, eight subjects (four women and four men) were sealed inside, living on food crops grown within. Due to an unplanned shortage of food, their diet became low in calories (averaging 1780 kcal/day), low in fat (10% of calories), and nutrient-dense. This ratio conforms to that which in numerous animal experiments has promoted health, retarded aging, and extended maximum lifespan.
After 6 months inside the Biosphere, the subjects' weight dropped from 74 to 62 kg (men) and from 61 to 54 kg (women). Mean systolic/diastolic blood pressure dropped from 109/74 to 89/58 mmHg. Total serum cholesterol dropped from 191 to 123 mg/dl; high density lipoprotein dropped from 62 to 38 (risk ratio unchanged); triglyceride levels dropped from 139 to 96 mg/dl (men) and from 78 to 114 mg/dl (women); and fasting glucose dropped from 92 to 74 mg/dl.
There is very little doubt that the drastic reductions in cholesterol and blood pressure may be instituted in normal individuals in Western countries by application of a carefully chosen diet. It is also relevant that a low-calorie, nutrient-dense regimen results in physiological changes in humans similar to those in other animal species.
Existing long-term data on humans is thin. Most human populations that are forced to survive on low-calorie diets are also malnourished and are as likely not to die prematurely from vitamin and mineral deficiencies. The only known exception is on the Japanese island of Okinawa. The Okinawans have about 70 percent of the calorie intake of the rest of Japan. They eat mainly fish and vegetables. In Okinawa, up to 40 times more people, aged over 100, than the rest of Japan. They also have less incidences of diabetes, tumors, and other diseases than the rest of Japan.
The typical American consumes 2 pounds of food a day. This equates to 700 pounds a year and about 230 tons of food over a lifetime. The typical meal consists of 1,200 calorie, of which 43% is fat, 11% is protein, and 46% is carbohydrate.
The calorie restriction diet closely resembles the Mediterranean diet and consists of 750 calories per meal, with 20% calories from fat, 20% from protein, and 60% from complex carbohydrates, such as fruits and vegetables.
