DNA can undergo changes not only in sequence, but also by the addition or removal of chemical groups. Such 'epigenetic' changes affect gene regulation and are thought to be involved in many diseases. Daniele Fallin and Andrew Feinberg at Johns Hopkins University in Baltimore, Maryland, and their colleagues have identified four genomic regions in which methyl-group abundance correlates with body mass index (BMI), which can indicate obesity.

The authors studied blood samples taken from 74 Icelanders on two occasions, roughly 11 years apart. They teased out 227 genomic regions in which methylation varied greatly across the volunteers. Of these, 119 remained unchanged within individuals during the 11-year period. These included the four regions linked to BMI, which were in or near genes implicated in obesity or diabetes. The authors suggest that stable epigenetic 'signatures' could provide personalized indicators of disease risk.

Sci. Transl. Med. 2, 49ra67 (2010)