While there are numerous factors in anti-aging health, one of the most important is nutrition. "You are what you eat" is more than just a saying: what you eat affects everything from your bones and muscles, to your organs and memory. Unfortunately, the typical American diet is not a healthy one. It contains too much fat, not enough fresh fruits and vegetables, too little fiber, too much processed food, and too much food overall, especially when it is combined with too little exercise as it often is.

There is considerable scientific study behind caloric-restriction diets, which may provide breakthroughs on anti-aging and the effect of diet on longevity. Research began in the 1930s at Cornell University, where rats on caloric-restricted diets lived 33 percent longer than those eating more calories. Other studies followed, on everything from worms to monkeys, and the results were the same: not only did animals eating less live longer, but they were virtually free of all diseases normally associated with older individuals, including diabetes, heart disease, neurological disorders and osteoporosis. In a 20-year experiment on monkeys, those on a caloric-restricted diet not only lived longer, but had brains that functioned like those of much younger animals.

In 1991, eight scientists spent two years in Biosphere 2, a sealed terrarium in Arizona that was, in theory, a self-sustaining ecosystem. Although the Biosphere didn't work as well as expected, it did help to validate the low-calorie diets the scientists ate. They lost weight, their cholesterol levels dropped, their blood pressure improved, and they were healthier than when the experiment started. In a 2004 study, subjects who had followed caloric-restricted diets for a long time had cholesterol levels that were the same or better than those of average Americans in their 20s, even though the youngest participant was 35 and the oldest was 82.

Quite simply, excess weight shortens the lifespan, and poor eating is the overwhelming factor in excess weight. A study of Okinawa, the Japanese district with the world's longest average lifespan and the highest percentage of people living to 100 or more, found that residents eat up to 40 percent fewer calories than Americans, and 17 percent less than other Japanese. Compared with Americans, elderly men and women in Okinawa are 75 percent more likely to retain their memory, and have 80 percent fewer heart attacks.

Very low-calorie diets aren't for everyone: they require considerable willpower and consistent meal planning. Such a diet also needs to be properly balanced. Drastically cutting back the amount of food eaten isn't enough; it has to contain the correct proportion of vitamins, minerals and nutrients, achieved through the right foods and supplements.

Even if taking the plunge to a caloric-reduced diet isn't for you, scientific studies prove that reducing your food intake is possibly the most important step you can take in your anti-aging regime. Just cutting back on foods that provide calories without adding sufficient nutrition, such as overly processed food and snacks, will help make a difference. It's fine to say that eating everything you like right now is one of life's great pleasures, but even better is staying healthy right to the end of a long, full lifespan.