Comment by tails4e

I've always been curious about my own metabolism. When I was a teenaeger / in university I ate pretty badly. Chocolate bars every day after lunch, loads of carbs, not to mention alcohol, etc etc. I was rail thin. I once got a body fat assesment when I joined a gym (I did no exercise at all and this was a brief attempt to get buff) and the person doing the test was shocked and couldn't pinch anything to measure. I had no fat. This lasted till I was 25 where seemingly overnight I then had to watch what I eat or I started to gain fat. So what explains this seeming inability to gain weight no matter what I ate, and in my mid twenties having a more normal response to junk food?