With about 60 percent of Americans officially fat, there’s plenty of blame to go around. Scientists at Duke University have just found another factor to join the ranks of trans fats and fast food: your mother. Tweaking the diet of pregnant mice had a substantial influence on their offspring’s gene expression—specifically, the expression of a gene responsible for obesity. And adding a soy isoflavone to the mothers’ diets during pregnancy limited the expression of the gene in utero, leading to babies half the weight of their soy-starved counterparts. But keep your maternal grudge in check: The human variant of the gene doesn’t seem to be susceptible to the benefits of prenatal soy. —Eric Mika