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.
The Navy actually relaxed their standards because they were kicking out too many otherwise qualified sailors. These days if you can suck in your gut to 39" or less, you're good to go.
The problem with the Navy (at least on the aviation side of things) is they no longer make the time to do command PT. They're too busy meeting a flight schedule. They're basically telling their sailors to work a full day and find time on your own to stay in shape. The end result is a lot of fat sailors.
And then there's the high carb Navy chow...