"Physical education, as typically provided, has not been shown to reduce or prevent obesity," write the study authors.
"That doesn't take away the fact that physical activity has been consistently associated with decreasing childhood obesity," says Krista Casazza, the lead study author.
"But the way physical education is currently given in the schools is the issue. Oftentimes, it's just kids going outside or being in a physical education class. It has to be an actual, purposeful event."
6. Breast-feeding reduces child obesity
"Although existing data indicate that breast-feeding does not have important anti-obesity effects in children, it has other important potential benefits for the infant and mother and should therefore be encouraged," write the study authors.
7. Sex is a good workout
Well, depending on how you do it.
The researchers cite evidence that sex takes about as much exertion per minute as going for a walk, but lasts on average about six minutes. That adds up to about 21 calories, which isn't such a good workout, but may be good for stress relief.
"Does it make any difference if you do calorie labeling? Does it make any difference if you cap soda size? Does it make any difference if you remove food advertising to children from television?" says Marion Nestle, professor of nutrition at New York University who is not associated with the study.
"Those are the really important things that people are looking at to change the environment of food choice to help people eat more healthfully, and I don't see any of that in here."