A: I agree that you just can’t control your stepson’s diet when he’s not at your home, but at the same time, I think you’re very wise to help him eat properly when he’s with you. Every little bit helps. Since it may seem unfair to an 8-year-old boy that he is asked to eat different foods than his stepbrother, it's a good idea to offer both boys the same foods as much as possible.
The great thing about wholesome, nutritious foods—such as fruits, vegetables, whole grains, beans, and lean meats—is that they’re good for kids who are both underweight and overweight. Most fruits and vegetables are so low in calories that it’s not necessary to restrict a child’s portions, and your stepson can fill up on those whenever he’s hungry. You can serve cut-up veggies with low-fat dressing in your stepson’s favorite flavor or fruits with his favorite flavor of low-fat yogurt. As far as milk, explain to your stepson that whole milk is for younger children, and because he’s a bigger boy now, he gets to drink the low-fat milk, just like the adults in your house do
Although your underweight son might be able to handle the extra calories from deserts and sweets, it would probably be best to serve lower-calorie treats when your stepson is visiting so that he doesn’t feel cheated. It’s always a challenge for moms to cater to children with different dietary needs, but with a little experimentation, it can be done. In your case, you’ve already identified the most important issue—avoid making your stepson feel that his brother is getting special treatment. Hopefully as your stepson gets older, he’ll learn to enjoy and appreciate the benefits of the nutritious foods that you offer him.