Fluffy dog.

Our little dog just seems to be getting rounder and rounder. Despite being fed what is an appropriate amount each day she continues to gain weight. I am wondering if she needs weight loss supplements? I suspect the root of her weight gain is my children. They are forever leaving snacks and treats out within her reach. I was starting to worry about my younger son when he constantly seemed hungry. I later realized that he was feeding his sandwiches to the dog and then asking me for another one. I am not sure what the answer to my problem is but it seems to start with training my children rather than the dog.