Do low-calorie, low-fat diets make you live longer? Studies on a wide variety of species, including primates, rats, mice, and spiders – show that caloric restriction increases life span and provides enough vitamins for good health.

This idea was first popularized in the 1960s by UCLA professor Dr. Roy Walford. Low caloric consumption reduces metabolic rate, blood pressure, fasting blood sugar, cholesterol and markers of inflammation, which are linked to early death.

Undereating is clearly not an American fad, but is interesting to scientists. Researchers from the Washington University School of Medicine reviewed the literature on studies examining the effect of low-calorie diets on measures of longevity.

They concluded that no evidence exists showing that caloric restriction extends maximum life span or life expectancy in humans.

However, people following these diets showed reduced risk factors for diabetes, cardiovascular disease and cancer, which suggest they may prevent premature death. [sources: Journal of Clinical Endocrinology & Metabolism, Fitness RX]