Our almost 14 year old son has been on meds since he was 5 because his ADHD is more severe than what you’ve described. Around age 11 he became interested in basketball. I can tell you that being medicated (pretty high dosage) has not affected his being hyper focused on his sport at all. He is still just as obsessed as a kid could be really. And his appetite is perfectly normal now but was definitely lessened the first several years. Maybe since your son won’t need as high of a dosage his appetite won’t be affected as much as higher dosages.
I also feel the need to interject that doing well in school is always more important than sports even when there is athleticism there. He may get injured and needs his education to fall back on.. therefore medication is certainly worth trying at least.