a scrawny guy xDDD
no, author, everything is fine with you now, right?) eat as much as you can) just don't be surprised when you're 40 and have a belly... and even more so, don't be surprised if you get chubby when you retire:)
I also have a fast metabolism, I don't gain weight easily from food... and yes, it's better to be fit, it's more pleasant, and you can gain weight if you want:) but losing excess weight is sometimes more difficult. and it's definitely more unpleasant to do crunches than to eat another chicken thigh ;D