Cutting calories may boost your lifespan

People who substantially cut their calorie intake develop some of the traits associated with longevity discovered in animal tests, a new study reveals.

Cutting calories reduced body temperature and levels of the metabolism hormone insulin, as well as decreasing DNA damage, showed the study. But follow-up tests are necessary to find out if these biological effects, which occurred relatively quickly, last for more than a few months.

Scientists hoping to understand the biological mechanisms that control ageing have increasingly given attention to the idea that reducing food intake can extend life.

Studies in rodents and other lower species have shown that long-term calorie restriction can boost longevity – increasing the maximum lifespan of mice and rats by about 30% and protecting them against blood vessel plaques and cancer. But with less experimental data from humans, researchers remain undecided about what to recommend to people.

Eric Ravussin of Louisiana State University in Baton Rouge, US, and colleagues conducted a trial with 48 volunteers randomly assigned to maintain their weight or reduce their calorie intake.

Calorie burning

Twelve of the people recruited for the trial ate enough food to maintain their weight. Of the remaining 36 people, an equal number were assigned to either cut their calorie intake by 25%, cut their calorie intake by 12.5% and burn 12.5% more calories with exercise, or to follow a stringent diet of just 890 Calories a day (until they lost 15% of their start weight, followed by a weight maintenance diet).

Participants received their prescribed meals at the research centre for the first three months of the experiment. The volunteers also attended weekly group meetings and had mid-week telephone calls to help them stick to their diets.

People on the caloric restriction diets lost an average of 10% or more of their weight. The researchers also found that these subjects had reduced fasting levels of the hormone insulin, a trait associated with longevity in animal research.

They also found that volunteers who restricted their caloric intake by 25% or achieved similar results by cutting calories and upping exercise had a reduced average core body temperature at the conclusion of the six month trial. Lower body temperatures are also associated with longevity.

Each of the low calorie groups also showed a small but statistically significant reduction in DNA damage in their blood cells, when compared with the control individuals. This is noteworthy, the researchers say, because some of the chemical by-products of food metabolism attack DNA, which might contribute to cancer and accelerate the effects of ageing.

Journal reference: Journal of the American Medical Association (vol 295, p1539)