Speaking Wednesday at a forum sponsored by Newsweek magazine, Mrs. Obama said that every parent is familiar with the difference in a child’s behavior when a child has had a healthy meal and when he or she has eaten a lot of sugar.

Mrs. Obama calls “extreme” the idea of requiring warning labels on unhealthy foods. She says that it is more important to give parents information on the ingredients in sugary snacks and how many of them can safely be included in a child’s diet.