According to a new study conducted by the University of Michigan, children are less likely to be obese if they have a younger sibling. Researchers aren't quite sure why this is, but we assume it's the sheer number of calories you burn fighting with a bratty little sib.
This data fits in interestingly with a larger study conducted last year in Sweden, which found that although older sisters have a lower BMI at birth, they are 29 percent more likely to be overweight as adults. The University of Michigan study only tracked the weight of children ages 1 through 6.
The Swedish study speculates this is due to physiological factors, specifically how the placenta changes between a woman's first and second pregnancy. University of Michigan researchers surmise that the reason older siblings are slimmer than their only children counterparts is because of behavioral changes: Older siblings are more likely to burn calories while playing with their siblings. According to Cosmopolitan, another study conducted by the NIH found that "moms put more pressure on only children to watch what they eat, which could make them rebel by eating more — hence their added weight gain."
What do all these studies mean for parents? Have as many kids as possible ... or just make sure your kids eat well without food-shaming them.