People who are fat and fit live just as long as their slim counterparts and are less likely to die from heart disease, according to a new study.

Researchers looked at 6,000 obese Americans over a 16-year period and compared their death rates with those of lean individuals.

Study leader Jennifer Kuk, medical doctor at York University in Toronto, Canada, said: “Our findings challenge the idea that all obese individuals need to lose weight.

“Moreover, it’s possible that trying – and failing – to lose weight may be more detrimental than simply staying at an elevated body weight and engaging in a healthy lifestyle that includes physical activity and a balanced diet with plenty of fruits and vegetables.”

Healthier obese people were generally heavier in early childhood, happier with carrying extra weight, and less likely to try to lose weight during their lives, said the researchers.

These individuals were also more likely to be physically active and to consume a healthy diet. The purpose of the study was to look at a new grading tool for assessing weight and health risk.

The Edmonton Obesity Staging System developed at the University of Alberta in Canada provides five stages of obesity. These are based both on traditional physical measurements, such as Body Mass Index which relates weight and height, and clinical signs of obesity-related medical conditions including diabetes and heart disease. The first two obesity stages were not associated with higher death rates.

“The finding that there were no differences in all-cause mortality risk between obese individuals in EOSS stage 0/1 and normal-weight individuals brings into question whether weight loss is beneficial for reducing health risk in this unique obese population,” the researchers wrote.