[Genomwide association studies on obesity: what can we learn from these studies]

The introduction of genome-wide association studies resulted in a tremendous increase in the number of genes associated with obesity and related phenotypes (BMI, waist and waist-hip-ratio). Despite this enormous gain in knowledge the search for genes is only started since only a small fraction of the heritability of these phenotypes is explained yet: each single gene of the 97 hitherto known BMI-associated genes and 49 waist-hip-ratio-associated genes explains only a tiny fraction of the variance of these phenotypes. Sex-specific differences are mainly known for waist-hip-ratio and ̴40% of the genes showed only an effect in women but no or a markedly smaller effect in men. The functional characterization of the identified genes will take a lot of time. It is unclear whether and how fast the findings will result in therapeutic consequences. It is of utmost importance that we understand the involved mechanisms before new therapeutic strategies can be developed.