Calories are a measure of energy in food. A small study has found that people improved their health when they severely restricted the amount of calories they ate. The study found that the people reduced their risk of heart attack, stroke and diabetes. Such risk normally increases with age.

Researchers at the Washington University School of Medicine in Saint Louis, Missouri, led the study. They say lower risk of disease means that the people can expect to live longer than average lives. The results appeared in the Proceedings of the National Academy of Sciences.

Researchers compared people who ate a traditional Western diet with people who ate fewer calories. They found that those who restricted their calories had less chance of blocked arteries. Fatty material can block the flow of blood to the heart and brain, and cause a heart attack or stroke.

The researchers found the people for the study through an organization called the Caloric Restriction Optimal Nutrition Society. Members of this group try to eat between ten and twenty-five percent fewer calories than the average American.

Eighteen members took part in the study. Their ages were thirty-five to eighty-two. They had lived on restricted calories for between three years and fifteen years. Doctors compared them with a group of people who ate normally.

The calorie-restricted group ate between one-thousand-one-hundred calories and about two-thousand calories per day. The amount depended on their weight, height and sex.

Twenty-six percent of the calories came from protein. Twenty-eight percent came from fat. And forty-six percent came from complex carbohydrates, such as whole grains.

The other group ate between about two-thousand and three-thousand-five-hundred calories per day. Eighteen percent of their calories came from protein. Thirty-two percent came from fat. And fifty percent came from carbohydrates. These included processed sugars and grains.

The researchers tested both groups for signs of blocked arteries. The team measured blood pressure and levels of several chemicals in the blood, including cholesterol and triglycerides. The doctors said some of the people who ate fewer calories had results like those of people many years younger.

This VOA Special English Health Report was written by Jerilyn Watson.