Four studies published in the Archives of Internal Medicine on Monday showed that if you want to stay physically and mentally healthier in old age then better start exercising.

According to a study by researchers at the Harvard School of Public Health, Brigham and Women's Hospital and Harvard Medical School, women who exercised more during middle age by had lesser chances of of developing a serious disease after 70.

Second study stated that there was improvement in attention spans and conflict resolution skills by a year of resistance training.

Third study found that people aged 55 or more who were into a moderate or high physical activity were able to fight cognitive impairment better.

Doctors believe that the studies conducted in Canada, Germany and the United States, could push more Americans to exercise.

Authors of one of the study said, "Since the American population is aging rapidly and nearly a quarter of Americans do not engage in any leisure-time activity, our findings appear to support federal guidelines regarding physical activity to promote health among older people."

Richard Cooper, co-author of a study and chairman of the Department of Preventive Medicine and Epidemiology said that people might be burning calories by exercising but they consume more than they burn and this where the problem creeps in.