There have been no formal studies of calorie restriction in humans. We know caloric restriction works for mice and fruit flies because they have such short life spans; a study that aimed to duplicate the results in humans would take decades. It's very hard to imagine a person volunteering to go hungry for much of their life when long-term benefits are still unknown.
Still, we have some basic anecdotal evidence that such a regimen might have benefits. In Okinawa, Japan, for example, which counts many centenarians in its population, people have traditionally consumed fewer calories. After World Wars I and II, when food was in short supply, fewer people died from aging-related diseases such as coronary artery disease, Type 2 diabetes and cancer [source: Hochman]. When researchers in the self-sustained Biosphere II found themselves running low on food in the 1990s, they adopted a calorie restricted diet; one of the researchers, Roy Walford, became one of the leading proponents of calorie restriction, writing books such as "The 120-Year Diet" and "The Anti-Aging Plan." Walford died in 2004 from amyotrophic lateral sclerosis (ALS, more commonly known as Lou Gehrig's disease).
Even without scientific evidence of the longevity benefits, plenty of people have adopted calorie restriction in the hopes of slowing the aging process. One calorie restriction advocate shared his daily diet with the New York Times in 2003:
- Breakfast: a megamuffin, a homemade concoction consisting of about 30 ingredients including raw wheat germ, rice bran, brewer's yeast, one carrot, strawberries and psyllium husk (the active ingredient in Metamucil)
- Lunch: a protein bar or a roast beef sandwich, hold the bread (simple sugars and flours are the first to go in a calorie restricted diet)
- Dinner: a serving of broccoli, zucchini and canned pink salmon, totaling exactly 300 calories, followed by a dessert of fruit salad topped with whey protein
It should be noted that this diet wasn't shared by the man's wife or children, which must only add to the work involved in this routine. Calorie restriction can seem like a full-time job that includes measuring and weighing food, learning about which foods pack the nutrients without the caloric punch and tracking consumed calories while maintaining a balance of carbohydrates, proteins and fats. It can also be expensive, since it involves lots of fresh vegetables and obscure grains available only from high-end brands.
Again, there have been no formal studies of how caloric restriction works in humans. Still, some scientists think they have an idea of how many more years a lifetime of megamuffins will buy you.