Ah yesssss, to once again have the metabolism of teenager! Life can be unfair to us old guys
Ain't it true.
My oldest daughter is 5'9 and slender - her freshman roommate was a tiny little gal who is about 5'1" and might weigh 110 pounds. She eats like a lumberjack and her metabolism burns it up.
Once time when they were freshmen, they were eating in the dorm cafeteria and happened to be sitting next to a table full of football players - big, buff, muscular guys who they knew just to say hello to.
It happened the tiny roommate was really hungry that night - she was chowing down with enthusiasm, until she looked up and saw that most of the football players were looking at her and some were shaking their heads. One of them said with a big smile: "Damn, girl, you can really pack it away!"
She turned bright red...but it's true.