Correspondence (letters to the editor): Waist–Hip Ratio More Appropriate Than Body Mass Index

The body mass index (BMI) does not say anything about a person’s body fat distribution. Without having observed a test person physically (either in person or in a photograph), using BMI is of limited relevance even for epidemiological studies. In addition, it can be assumed that quite a few lay people simply calculate their BMI incorrectly or misjudge it. This would easily explain the variability, the risk of bias, and the inconsistency in the results of relevant studies (1).

Even when looking at individual cases, BMI can actually only be used validly if the appearance of the test person is known. The best example are well-trained strength athletes, such as boxers or bodybuilders. Without having specific knowledge about them, these athletes would routinely be classified as obese based on their BMI: an athletic muscular heavyweight boxer who is 2 m tall and has an “ideal” combat weight of 120 kg would have a BMI of 30 (e.g., at the border between being overweight /obese).

For adults who are overweight, having fat at the height of the belly button (waist) increases their risks of developing cardiovascular disease and diabetes mellitus as well as of premature death (2). The so-called waist–hip ratio (WHR) can reveal an unfavorable increase in abdominal fat much better, and is also easier to calculate, than BMI. Interestingly, the self-assessed BMI of participants in a large US study correlates well with certain biomarkers, such as triglycerides and leptin, but less so with a more precise classification of the prevalence of obesity (3). In our opinion, (self) assessment of health risks from obesity would be more accurate if at least both BMI and WHR were always calculated in parallel.