While average BMI has increased over time in most countries, the prevalence of cardiovascular risk factors may be decreasing among obese individuals.
In a study appearing in JAMA, BĂ¸rge G. Nordestgaard, M.D., D.M.Sc., of Copenhagen University Hospital, Herlev, Denmark and colleagues examined whether the body mass index (BMI) value that is associated with the lowest all-cause mortality has increased in the general population over a period of 3 decades.
Thus, the BMI associated with lowest all-cause mortality may have changed over time. This study included three groups from the same general population enrolled at different times: the Copenhagen City Heart Study in 1976-1978 (n = 13,704) and 1991-1994 (n = 9,482) and the Copenhagen General Population Study in 2003-2013 (n = 97,362). All participants were followed up from inclusion in the studies to November 2014, emigration, or death, whichever came first.
The authors write that an interesting finding in this study is that the optimal BMI in relation to mortality is placed in the overweight category in the most recent 2003-2013 cohort. "This finding was consistent in both the whole population sample (optimal BMI, 27), and in a subgroup of never-smokers without history of cardiovascular disease or cancer (optimal BMI, 26.1). If this finding is confirmed in other studies, it would indicate a need to revise the WHO categories presently used to define overweight, which are based on data from before the 1990s."