Australasian Science: Australia's authority on science since 1938

Overweight People Don’t Live Longer

Overweight people don’t live longer than those with a lower body mass index (BMI), according to research published in PLOS ONE.

Previous research led to conflicting conclusions about whether overweight people can live longer, so researchers examined the way in which data were analysed in a range of studies. “The clear truth is that people who are overweight or obese have a higher risk of premature death,” said lead author Dr Grace Joshy of the Australian National University’s National Centre for Epidemiology and Population Health (NCEPH). “It is a pretty simple truth, especially given the clear evidence that the risks of cardiovascular disease and cancer, Australia’s biggest killers, are higher for those who are overweight or obese.”

The ANU-led study looked at factors such as the width of the BMI categories used and pre-existing illness to examine why some studies suggested a link between longer life expectancy and being overweight.

Joshy said studies suggesting that overweight people live longer did not take into account other major health factors. “These studies failed to take into account the fact that many people with a healthy weight can still be quite unhealthy as they might smoke or be trim because they are actually sick,” she said.

Professor Emily Banks of NCEPH and the Sax Institute, who was a senior author on the study, said that the studies that produced the misleading positive findings about being overweight had compared the risk of death in overweight and obese people with the risk in a large “mixed bag” of thinner people.

“Overweight people looked good by comparison, but when you account for illness and look in detail at how the risk of death varies gradually with BMI, you find that the best BMI to be is relatively lean, at around 22.5–24.9,” she said.

Banks said that in Australia “around 63% of adults are overweight or obese”.