On a calorie-restricted diet, you'll eat far fewer calories than your body needs to maintain your normal weight. Research has shown that such a lifestyle has significant potential to slow the aging process and provide other health benefits in addition to weight loss.
History
Studies with worms, mice and monkeys since the 1930s have shown that animals on a nutritious diet with half the calories of a control group lived almost twice as long as their better-fed peers. The calorie-restricted diet for humans was pioneered by Dr. Roy Walford, author of the 1986 book "The 120-Year Diet," who also formed the Calorie Restriction Society, which has 7,000 members and another 100,000 adherents practicing the diet worldwide.
Identification
The calorie-restriction diet isn't designed specifically to be a weight-loss diet, although that may be a positive side effect. Its purpose is to prevent various diseases plaguing modern society, which have been tied to a poor diet, and to provide slower aging and an extended lifespan. Generally, a calorie-restriction diet calls for 20 to 30 percent fewer calories than usual and involves focusing on high-density, low calorie foods.
Benefits
Preliminary research of humans on the calorie-restriction diet indicate it can lead to lowering your blood pressure, blood sugar levels, body fat percentage, cholesterol levels and weight. Some studies also suggest a calorie-restriction diet can improve memory in older adults. Although Dr. Walford believed that the diet could extend your lifespan up to 160 years--depending on when you start and how thoroughly you hold to it--these beliefs are controversial, with some experts estimating a long-term calorie-restricted diet may only increase your life expectancy by four to 17 percent, according to the Mayo Clinic.
Features
The Calorie Restriction Society recommends filling up on bulky foods high in nutrients but low in calories, such as most vegetables and fruits, in order to stave off hunger and get all the vitamins and minerals your body needs. Low-fat protein choices might include lean beef, turkey or chicken, fish, low-fat dairy, soy and egg whites. Fat is a very calorie-dense nutrient, but it also helps to make you feel less hungry, so foods such as nuts, avocados and olive oil are added into your diet in small amounts.
Expert Insight
A 2004 study at the Washington University School of Medicine by John O. Holloszy et al and published in the "Proceedings of the National Academies of Sciences" found that calorie-restriction subjects scored vastly better on all major risk factors for heart disease including total cholesterol, triglycerides, and blood pressure, as well as lower levels of C-reactive proteins that are linked to inflammation in your body. In 2009, a 20-year study on rhesus monkeys fed a calorie-restricted diet by a team led by Ricki J. Colman and Richard Weindruch at the University of Wisconsin was published in the journal "Science." The team reported that the monkeys are showing many beneficial signs of caloric resistance. Leonard Guarente of the Massachusetts Institute of Technology believes these effects are due to the fact that an organism responds to food scarcity by slowing aging and reproduction to survive.
Warning
The Mayo Clinic recommends that if you want to try a calorie-restricted diet for anti-aging that you consult your doctor first to make sure you get enough nutrients. Side effects of the diet may include menstrual irregularities, hormonal changes, reduced bone density, loss of muscle mass, anemia, dizziness, depression, irritability, lethargy and edema. Research in 2009 by David Schneider et al at Stanford University found that a calorie-restricted diet may weaken the immune system in some cases, and a team at led by Raj Sohal of the University of Southern California's School of Pharmacy reported that naturally chubby mice lived longer on a reduced-calorie diet, but naturally lean mice did not.
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