The vast majority of people who show up for Basic Training are unfit for military service. That’s why they get sent to Basic Training. Most of them are OK on the far side.
No truer words. I enlisted and went to basic on my 17th birthday. A hopeless classic juvenile delinquent. Of course this was mid 60's when a DI could and would knock you on your keister for being a F-up, if he wouldn't your barracks mates would. After Basic, was a different person entirely.
Basic does break you down and build you up; but, the problem is after that where you’re given freedom and not forced to run and march miles a day.
I was in the Navy from 2002-2008, and the amount of morbidly obese people in the Navy was shocking to me. I doubt it’s gotten any better.
The Marine Corps. is the only branch that still enforces “military appearance” with passion.