It's true.
I was a NEET for a year, had massive savings from my job and... well, as my weight increased and passivity set in, I was down bad. Like, tying noose down bad.
My back was killing me so I went to the doctor and he said my lower back basically has no muscle and there was a real danger in sustained permanent disability due to how tall I am. That was it, got gym membership and 6 months later... man. The grass did become greener.