Working out can get you into bad habits, martial arts and boxing and weight lifting are social but can lead to trouble
So if you don’t have medical insurance try signing up for medical insurance from the state or county (I live in contra costa so I have medical) for free health insurance. After the free health insurance you have to sign up for health care, and chances are it won’t be fabulous, so I’d ask a parent to get you health insurance
There you can talk to someone who knows you medically and can get you a dietitian so you can be slim or fit
They can even fix irritable bowl syndrome which makes people gassy around certain people