Here’s a quick look at two studies which highlight the value of children playing outside.

The first study concludes what really should be obvious: Children between the ages of 3-5 with no access to outdoor play areas, parks, or gardens are more likely to be overweight or obese by the time they are 7 years old. Many children live in apartments and high-rises where there may be limited outdoor play spaces. Others live in neighborhoods which are unsafe, their playgrounds and parks too dangerous to play in. Commonly, children have parents who model sedentary activities and don’t themselves seek out outdoor activities and exercise. The result is that these kids have a higher risk of experiencing the social and economic consequences of overweight and obesity, as well as the health risks, including type 1 diabetes, heart disease, stroke, and cancer.

One-third of children in the United States are either overweight or obese, very similar to the 6,500 English children who participated in the study.

The second study, published in JAMA, involved more than 1,900 Chinese schoolchildren over a three-year period. It showed that adding 40 minutes of outdoor activity per day at school diminished the students’ risk of developing myopia (shortsightedness) compared with children who were not given the opportunity for additional outdoor play. Maggie Fox reports that the myopia was reduced by 23% in the outside group:

The researchers don’t think it’s exercise alone, or time spent away from books and computers alone, that’s making the difference. In a study in which kids were assigned to exercise indoors, rates of myopia were not affected, they said.

It’s not clear what it is about being outdoors that might affect vision — exposure to sunlight, forcing the eye to focus on objects a varying distance away, exercise, or a combination of these factors.