Patty is gaining a lot of weight... advice?

[crystalite]

I took Patty to an avian vet for a checkup and they said he's a little on the chubbier side (images attached). He's 7 months old. Apparently, his breastbone can barely be felt and he looks great overall. He usually flies to me with or without command, but now he's very hesitant about it and tries his best to lift off. He instead walks over. I think it's because he's worried about falling, but I'm not sure. He eats Harrisons, his veggies, and the occasional fruit or millet as a treat. He also has 1-2 hours of outside cage time a day. I'd like to incorporate some exercises, do you have any suggestions?
Thank you!