Genetic and epigenetic mechanisms in obesity

Obesity is a relevant medical problem. Around 60 % of German adults are overweight, 20 % are obese. The hereditary contribution to the variance of body weight is high. Nevertheless, molecular genetic studies have as yet explained only a small part of the inter-individual variability in the body mass index (BMI). Monogenic forms of obesity, in which loss of a single gene product leads to extreme obesity, are very infrequent. Variance of body weight is commonly explained by a complex interplay of many genetic variants (polygenic obesity). Each variant contributes only a small amount to the body weight. Currently, the largest published analysis of individuals of European origin identified 32 genetic variations (single nucleotide polymorphisms, SNPs) associated with BMI (obesity). Overall, these polygenic obesity variants only explain about 5 % of the variance of the BMI. In addition to the DNA variants epigenetic factors seem to also play a role in body weight regulation. These epigenetic marks can change in the course of life. They might provide an interface between genetic and environmental influences. It is conceivable that in future it will be possible to use epigenetic and genetic markers to detect a predisposition for obesity and to improve prevention and therapy.