If obesity was all due to genetics, then we wouldn't be seeing the huge and rapid increase apparent today. However, although the obesogenic environment is a major factor, some estimates suggest that genetics could be responsible for as much as 50% of the problem. If that's true, what is the mechanism? There is increasing evidence that behavioural, rather than metabolic factors might be important, and that these may operate from a very early age. Two related studies published in JAMA Pediatrics add support to this view. Both are …