After a food-filled holiday, losing weight often tops the list of popular New Year’s resolutions — but a new study is shedding a different light on those extra pounds.

A U.S. study, published Wednesday in the Journal of the American Medical Association, looked at nearly 100 previous studies on weight and mortality, and found that overweight people have a significantly lower risk of premature death than those who are normal weight.

To track the finding, the team — led by the National Center of Health Statistics’ Dr. Katherine Flegal — looked at 270,000 deaths from a diverse array of countries including China, Australia, the U.S., Canada, Mexico and Israel.

The result was that people with a Body Mass Index of between 25 and 30 — considered “overweight” — were about six per cent less likely to die prematurely than those in the “normal” range, between 18.5 and 24.9. It also found that those at the lower end of “obese,” between 30 and 35 on the BMI scale, had a similar incidence of premature death as those in the normal range.

Less surprisingly, people considered “grossly obese,” with a BMI higher than 35, were 29 per cent more likely to die early than skinnier people.

BMI is calculated by dividing a person’s weight in kilograms by their height in metres squared. It is a common standard for measuring the weight of populations, but it often groups fit, young people in the overweight category due to the relative mass of muscle, explained Dr. Stephen Heymsfield on Thursday.

“There’s a correlation between body mass index and body fat, but it’s a weak correlation,” said Heymsfield, the co-author of an editorial that accompanied the study. “For example, there are people who are overweight who are not overfat… Likewise, there are people who are normal weight who are over-fat, so it’s an imprecise measure.”

He said overweight people who take refuge in the study’s results should be careful to pay attention to the details, noting it didn’t look at the overall health of overweight people, just whether they were likely to die or not.

“It doesn’t say anything about whether heart disease or diabetes is increased,” said Heymsfield, the executive director of Pennington Biomedical Research Centre in Baton Rouge, Louisiana. “It is possible that people could live longer with the disease than previously expected.”

Some scientists have suggested overweight people may be more likely to have regular doctor visits than people of normal weight, which might help detect illnesses earlier.

If the average person can take anything from this study, said Heymsfield, it’s the link between morbid obesity and death.

“I would definitely resolve not to gain more weight and go into that obese range,” he said, adding that those in the overweight range shouldn’t see the results as an excuse to ignore their health. “If you are overweight by Body Mass Index, it’s good to make sure you don’t have high blood pressure or any other risk factors.”