There have been hundreds of studies linking obesity to anything from depression to cancer. Here’s another not-too-surprising study which revealed that children who are obese tend to have lower math scores. The researchers’ explanations seemed to sidestep the possibility that being overweight can directly cause lower scores on math tests. They cite social and emotional factors being obese which could increase stress on the brain, which can lead to cognitive decline. What they failed to mention is the pink elephant in the room: Obese kids are much more likely to have untreated obstructive sleep apnea, which can lead to behavioral problems, mood disturbances, as well as poor performance on tests. I would think lack of oxygen on the brain is a major source of stress.