Hello @cbgirl123 and welcome to Mayo Clinic Connect. I completely understand this as I, too, have a teen boy. From the moment they start puberty, it was our experience that putting on weight becomes extremely difficult. In my son's case, he was growing so quickly and extremely active so putting on weight was next to impossible. He's slowed down growing slightly and is finally now able to put on a little weight. At 13 years old, he is just coming into the beginning stages of puberty I am guessing so this might be a challenge until he is through his growth spurt.

Some things we found to be helpful is to add in a protein shake each morning and we also switched from 2% to whole milk. It actually tastes creamier and better for protein shakes anyway! Bonus! Additionally, lots of protein and carbs is needed to fuel these young athletes! My son is good at protein but I had to push more carbs on occasion too.

There are tons of protein powder options and finding one he likes may be your biggest challenge. We rotate between vanilla and chocolate and add in frozen bananas and peanut butter with the chocolate powder and it tastes like a Reece's PB Cup!

Is this a concern for him as well as you?