My thoughts on "junk' or high sugar or fat food, is that everybody eats these as treats but I like to see the children in my daycare eat the healthy food first. The tuna, egg, peanut butter sandwich, the pasta, the left over stew, etc and the fruit, vegetables and yogurt are allowed before any treats. The young overweight girl I looked after years ago came with jam sandwiches, marshmallows, chocolate cookies, chocolate milk, cakes, and candies for lunch I am not too concerned with eating junk food if there isn't an imbalance leaning towards the goodies or treats.
My own boys have grown up with occassional treats and now that they are teen agers they prefer wholesome food to fat or sugary food. I can only hope that they carry on with these eating habits as they grow older.