WASHINGTON:

How much weight is healthy for a person depends on his or her gender, height, and body frame size. It is already known that maintaining a healthy body weight can significantly reduce the risk of a number of diseases, including heart disease, diabetes and depression. Healthy body weight has also been shown to improve the overall quality of life.

A new study in mice has revealed that keeping healthy weight limits brain exposure to insulin — a natural hormone made by the pancreas that regulates the level of sugar glucose in the blood, reported the online edition of BBC News. Reducing insulin signals inside brain cells of mice were found to increase lifespan and a healthy lifestyle and it may have the same effect on humans, scientists said.

Earlier studies in fruit flies and roundworms had suggested that reducing the activity of the hormone insulin, which regulates blood sugar levels, could increase lifespan. The latest study by scientists at the Howard Hughes Medical Institute looked at the effects of a protein, IRS2, which carries the insulin signal to the brain. Mice who had half the amount of the protein lived 18 percent longer than normal mice. Despite being overweight and having high levels of insulin, the mice were more active as they aged, and their glucose metabolism resembled that of younger mice. The researchers said the engineered mice were living longer because the diseases that kill them, such as cancer and cardiovascular disease, were being postponed due to reduced insulin signalling in the brain, even though circulating levels of insulin were high.

They said that in the future it might be possible to design drugs to reduce IRS2 activity to reproduce the same effect, although they would have to be specific to the brain. “Our findings put a mechanism behind what your mother told when you were growing up, eat a good diet and exercise and it will keep you healthy,” lead researcher Morris White said.