New Delhi, Jan. 21: An American study has bolstered a claim made 10 years ago by Indian scientists that eating less might delay ageing in humans.

Researchers at the Washington University School of Medicine, St Louis, have shown that the hearts of people who eat less resemble the hearts of younger people.

“Eating less, if it is a high-quality diet, will improve your health, delay ageing and increase your chance of living a long and healthy life,” said Luigi Fontana at the Centre for Human Nutrition at Washington University.

The US study is the first to show that food restrictions have a positive effect on the heart against the age-associated decline of heart functions.

The scientists studied the hearts of 25 people who had followed a restricted calorie diet (consuming 1,400-2,000 calories per day) for six years and 25 other people who were on typical western diets (2,000 to 3,000 calories per day).

As people grow older, their hearts tend to stiffen and pump blood less effectively. But ultrasound studies showed that the hearts of the people on restricted calories were more elastic than those on normal diet.

Their hearts relaxed in between beats in a way similar to the hearts of younger people. Certain risk factors known to be associated with heart disease, such as blood pressure and the levels of a molecule called the C-reactive protein, were lower in the restricted calorie group than in people on normal diet, according to the study published last Monday in the Journal of the American College of Cardiology.

Scientists have known for decades that animals live longer when fed fewer calories. “This is the first study ever to show that calorie restriction with optimal nutrition may delay primary ageing in human beings,” Fontana said.

Scientists in Hyderabad had claimed in 1996 to have observed for the first time the beneficial effects of chronic undernutrition against ageing in humans. They had published their findings in the journal Current Science.

Kalluri Subba Rao, a professor of biochemistry at the University of Hyderabad, and his colleagues had shown that a group of undernourished people had higher levels of certain enzymes that act against the routine ageing processes.

Rao had compared differences in these enzymes between people who were on a normal diet and undernourished people. They used the weights and the history of diet to classify a sample of population in Hyderabad into normal and undernourished groups.

“We had used a naturally available population of undernourished people to study the differences in ageing mechanisms,” said Rao, now emeritus professor at the Centre for Research on Ageing and Brain at the University of Hyderabad.

Scientists have cautioned that calorie restriction with a bad diet will only accelerate ageing and lead to severe disease. “Eating half a hamburger or half a packet of fries ... is not healthy caloric restriction and is harmful,” Fontana said.

The restricted calorie diet in the US study contained a variety of vegetables, olive oil, beans, whole grains, fish and fruit. People on this diet avoided refined foods such as white bread, soft drinks, and desserts with free sugars.

In overweight people, fat cells release inflammatory molecules into the bloodstream, exposing body tissues to inflammatory stimuli. Fontana said inflammation can cause tissue damage leading to premature or accelerated tissue and organ hardening.

Since the 1996 study on humans, Rao and his colleagues in Hyderabad have been pursuing studies on rats to decipher the molecular mechanisms of delayed ageing induced by restricted diet.