I know this question isn't related to calisthenics but I seriously want to know it. My little brother has a really fast and good metabolism, he stay lean whatever he do, on the other hand I have a really slow metabolism since pre puberty, what I do I remain around 20℅ bodyfat. Why? Both of us are same brothers with same parents yet our metabolism is so different and I have noticed it into my friends and their siblings too, one is fat and other is lean. I remember when I was a kid I used be skinny and I remember I had consumed some doctor prescribed pills related to my anger issues but I remember they didn't worked on my anger issue but they sure did gave me crazy weight gain and super crazy hunger, but this is really old episode of my life, maybe 8 to 9 years ago, what's the problem now?