Being “fat but fit” does not increase longevity

The widely publicised claim that life lasts longer for those who are modestly overweight is a myth, a new study has shown.

The idea that being “fat but fit” confers advantages comes from many observational studies suggesting that on average those whose body mass index (BMI) is slightly higher than ideal live longer. But, say Bristol University researchers, people are often thin because they are already ill with the diseases that will ultimately kill them. They don’t die early because they’re thin; they are thin because they are already ill or dying.

David Carslake and George Davey-Smith, together with other colleagues from Bristol and Norway, set out to test the relationship by comparing when people died not …