Most of my life I've struggled to maintain a healthy weight and the ADHD was a big part of that. What personally helped me was a book I bought called The PE Diet. Long story short, the book shows you how to replace high calorie foods that are not very filling with lower calorie options that are more filling. This really helped me, I can make a massive meal and follow that with snacks that are sweet enough and filling that are not calorically dense. I've also combined this with a calisthenics program (Also in the book) for maintaining flexibility and strength.
