Eat less, live more

DIETING according to an old joke, may not actually make you live longer, but it sure feels that way.

Nevertheless, evidence has been accumulating since the 1930s that calorie restriction—reducing an animal's energy intake below its energy expenditure—extends lifespan and delays the onset of age-related diseases in rats, dogs, fish and monkeys.

Such results have inspired thousands of people to put up with constant hunger in the hope of living longer, healthier lives. They have also led to a search for drugs that mimic the effects of calorie restriction without the pain of going on an actual diet.

Initial results of the first systematic investigation into the matter, known as CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy), was sponsored by America's National Institutes of Health.

It took 48 men and women aged between 25 and 50 and assigned them randomly to either a control group or a calorie-restriction regime. Those in the second group were required to cut their calorie intake for six months to 75% of that needed to maintain their weight.


The CALERIE study is a landmark in the history of the field, because its subjects were either of normal weight or only slightly overweight.

At a molecular level, CALERIE suggests these advantages are real.

For example, those on restricted diets had lower insulin resistance (high resistance is a risk factor for type 2 diabetes) and lower levels of low-density lipoprotein cholesterol (high levels are a risk factor for heart disease). They showed drops in body temperature and blood-insulin levels—both phenomena that have been seen in long-lived, calorie-restricted animals. They also suffered less oxidative damage to their DNA.

It was of no wonder that women lived longer than men.