How can you tell if you have a fast metabolism?

if you're able to eat a lot of whatever you want, don't exercise to burn off those extra calories, and you remain thin. it's usually either an indicator of a fast metabolism or a thyroid problem.

i don't know anyone who's heavy and has a fast metabolism, but then again, I don't know anyone who's been properly diagnosed with a fast metabolism...i tend to just assume that someone who can eat fast food and ice cream on a regular basis, and doesn't play a sport or go to the gym, has a fast metabolism.

I have a fast metabolism and I kinda hate it. Yeah, I can eat whatever I want and not gain, but I was made fun of for being skinny. You can tell if someone has a naturally fast metabolism if they eat a lot and don't gain. You can also tell by looking at pictures of when they were younger, and if they were skinny then and they're still skinny then they probably have a fast metabolism.