This article was about children at the age of ten who eat candy everyday. They say when they grow up they will end up being aggressive when older. They think this will happen because if you give little kids sweets everyday for absolutely no reason, they won't learn or understand how to wait for something you desire. Not being able to wait or put off what you want until you earn it can make them behave aggressively later in life.
http://www.sciencedaily.com/releases/2009/10/
I think that this article is right. I think that if you don't know how to wait for any reward or a praise, not just candy, can change your behavior for the worst. It says in the article, "Targeting resources at improving children's diet may improve health and reduce aggression." I believe that if you change the kids diet and give them a reward when they do something good, not just because their young and it doesn't matter can change the way they behave when they are older.