While the body mass index (BMI) has been a popular yardstick for deciding who is at risk of obesity-related diseases because of their weight, since it is essentially a measure of density, identifying 'under-' and 'over-weight' risk groups, a more sophisticated approach than BMI is needed, says a new study.

Manfred J Müller and colleagues at the University of Kiel in Germany explain in a recent article for F1000 Biology Reports how 'functional' body composition analysis (BCA) measures more of the variables that determine whether or not obesity is 'benign'.   Recent studies using similar analysis suggest that up to 30% of obese people do not require medical treatment, so widespread adoption of BCA could significantly improve the targeting of limited healthcare resources in the context of one of modern society's global killers.

With advances in imaging technology, variables such as the body's fat proportion, location and distribution and the size of fat cells and fat droplets within these cells can now be factored into the health risk assessment. 

Coupled with a better understanding of the interrelation between genes, environment, hormone levels and metabolism, BCA gives clinicians a clearer picture of the specific health risks to an individual.

In light of the growing evidence in favor of functional BCA, the authors conclude that "the definitions of both 'overweight' and 'malnutrition' should be reconsidered" by clinicians and researchers. Evidently, size does still matter but it's what you do with it that really counts.