I went to school in the 50s and 60s.I took a brown paper bag to school with me each day.Typically,it contained one(or two sandwiches),some fresh fruit,and something sweet.On fridays,the good sisters conducted"The Hot Dog Sale"to raise money for our parish,and(I think)to give us a break from the monotony of brown bagging it.There were some fat kids,but very few.I know times have changed,but......?
I think sedentary activities (Xbox and internet) are more to blame.