Just Don't work yourself to the bone.
DID YOU JUST DO WHAT I THINK YOU DIDAnyway, another fast-metabolism stick figure calling in--it really ain't as nice as it might sound (everybody wants what they don't have, after all, and it always sounds better than it might actually be because they want it). Being hungry quite literally
all the time is really unpleasant, and not being able to retain any weight just means the process of
"feeling famished even though you just ate an hour ago and junking on something that's probably crap for your body in the long run just to get your stomach to chill its shit because the growls and pangs have reached the point of nausea which makes it harder to want to eat and the pangs just get worse and the whole thing repeats itself endlessly" just continues on and on and on.
I'd love to be able to put on a bit of weight, if only to slow this shit down enough to be more tolerable; likewise, plenty of people I know sing praises of my metabolism like it's a godsend when it's really not all that nice. The only real silver lining is that I can basically eat whatever and be fine, but that leaves a whole wide realm of possibilities of putting bad shit in my body, so it isn't all THAT nice.
Strange thing is, I've quit smoking and the often-quoted "oh you'll put on a bunch of weight once you quit" hasn't made a single appearance thus far. Hell, last I weighed myself I was somewhere around 120, and the last time before that I was 135, so somewhere along the line about 15 pounds got away without me knowing and I don't like that.
Fast metabolisms burn calories off a lot quicker, but it's not some cure-all that fixes everything. It's just the other extreme end of the spectrum. Both extremes suck in their own right.