Ran across this article in our regional paper this morning: "Students get dumber and fatter during the summer." http://www.kentucky.com/2012/07/19/2263552/students-get-dumber-fatter-during.html#wgt=rcntnews
While we probably can blame the decline in academic performance to being out of school, the increase in weight would probably occur in the summer regardless of whether school was in session or not. Unlike the summers of my childhood in the 1950's, current summers are hotter (yes, climate change), and unlike the homes of my 50's childhood, most people's homes are cooler via the miracle of air conditioning, making outdoor play unappealing. Unless you have a pool, the attractions of the sedentary indoor life are greater than those of the outdoors in today's summers.