My 12 year old son is on a very strict diet and plays all sports- taking PE at school and is pretty active. My wife and I are very healthy cooks and work out. Our other two boys are skinny. He is rapidly gaining weight and it is concentrated in belly. We cannot figure out why as we do not drink soft drinks or have junk food in our home. He is a big kid, but it makes no sense for this type of weight gain.... 12 years old and 195 lbs.... Any advice????