A group of British scientists is reporting that overweight moms are not genetically "programming their children to be fat". The University of Bristol's Debbie Lawlor and her team wanted to see if the high levels of sugar and fatty acids in the blood of overweight women caused higher levels of those substances in the blood of their offspring, thereby predisposing their fetuses to "poor appetite control and a slower metabolism." Lawlor found that genetic link to be tenuous, though the children of overweight parents are still more likely to tip the scales. There is a "fat mass and obesity associated" gene called FTO, but it is unclear how this gene works in concert with outside dietary forces. The only conclusive result of the study seems to be that the effect of maternal Body Mass Index is more of an indicator of childhood obesity than the effect of paternal BMI. (Yeah, mom is always to blame.)
Lawlor's evidence implies that diet and exercise are the major factors in the childhood obesity epidemic, which is probably why maternal BMI has more of an effect than paternal BMI. Mothers are still the parents who tend to grocery shop and plan meals, so it's no surprise that overweight children are consuming the same unhealthy foods that their mothers do. "Our study indicates that developmental overnutrition has not been a major driver of the recent obesity epidemic," Lawlor concludes. "Therefore, interventions that aim to improve people's diet and to increase their physical activity levels could slow or even halt the [obesity] epidemic."