Overweight septuagenarians are less likely to die within 10 years than people of "normal" weight in the same age group, an Australian study found on Thursday.
The study in the Journal of the American Geriatrics Society followed 4,677 men and 4,563 women aged 70 to 75 for a ten-year period from 1996.
In addition to their "body mass index," or BMI, which estimates a person's body fat, the researchers also took into account the state of their health and their lifestyle.
Participants whose body mass index was classified as overweight were 13 percent less likely to die than those classified as being of normal weight.
The benefits, however, were seen only in those who were overweight but not obese.
"These results add evidence to the claims that the WHO (World Health Organization) BMI thresholds for overweight and obese are overly restrictive for older people. It may be timely to review the BMI classification for older adults," said Leon Flicker, of the University of Western Australia and the lead researcher.
Although excess pounds reduced the risk of death among both men and women over 70, a sedentary lifestyle was found to double the risk among women, and to bump it up by 25 percent among men.
"Our study suggests that those people who survive to age 70 in reasonable health have a different set of risks and benefits associated with the amount of body fat to younger people, and these should be reflected in BMI guidelines," Flicker said.
The body mass index is calculated by dividing a person's weight in kilograms by the square of their height in meters.
A body mass index of between 18.5 and 24.9 is considered normal. A person with a BMI of 25 to 30 is classified as overweight, and as obese if their BMI is over 30.