Andy is growing really quickly, but I'm afraid that he's starting to get a little bit too pudgy. He weighs 17 lbs. which is close to the sheltie standard. He's almost 6 months old. Right now he's on RC puppy. Should I go ahead and switch to him to adult formula? He's not really eating that much so I don't want to feed him less, but could changing to an adult formula keep him from getting any fatter?