A recent study using data from the UK Biobank has found that individuals with higher fat levels have an increased risk of cardiovascular events such as heart attack or stroke. In both men and women, a 5 kg/m2 higher body mass index is associated with a 13% increase in risk of cardiovascular disease. Similar results were observed for measures of central adiposity such as the ratio of waist circumference to hip circumference, commonly referred to as waist-hip-ratio. People with more fat around the waist relative to the amount of fat around the hips had a higher risk of cardiovascular disease, an increase of about 10% for a 0.07 higher waist-hip-ratio.
Some previous studies have found that, paradoxically, being overweight or obese appears to be protective for all-cause mortality compared with normal weight. However, these studies included, or were restricted to, people with prior disease. As individuals can lose weight after developing disease, it is likely that these findings are a result of bias rather than overweight or obesity conferring a true survival advantage. This is supported by the UK Biobank study, which excluded participants with prior disease to improve the reliability of the results for body mass index, and found that individuals who were overweight or obese have an increased risk of cardiovascular disease when compared to those with a body mass index in the normal range.
In her editorial in the current European Heart Journal, Dr Natalie Staplin suggests the associations between central adiposity and cardiovascular disease may be stronger than reported in the study. The difficulty in choosing where to measure waist and hip circumference makes waist-hip-ratio a less reproducible measure than body mass index but the analyses did not account for this. After correction for the measurement error in waist-hip-ratio, the increase in risk of cardiovascular disease associated with 0.07 higher waist-hip-ratio would be nearly double that reported. These findings highlight the importance of controlling adiposity to help prevent cardiovascular disease.