Average BMI associated with lowest risk of death increases

Researchers from Copenhagen University Hospital in Denmark recently examined whether BMI associated with the lowest mortality rates has increased in the general population over a period of 30 years and published their findings in JAMA. Previous work has suggested that whilst average BMI is increasing across most countries, the prevalence of cardiovascular risk factors is decreasing; the researchers hypothesised that the BMI associated with lowest all-cause mortality might have changed over this time period.

They found that BMI values have increased by a factor of 3.3 over three decades. This means that the optimal BMI in relation to mortality is in the overweight category (for the last cohort that they examined – 2003-2013). The authors have suggested that the WHO should revise the BMI values that currently categorise people into normal weight, overweight and obese, as the data to form these was collected before the 1990s. However, they acknowledge that further investigation is needed to understand the reasons for these changes as well as any potential implications.