He works South Central with the LAPD now. We didn't have any option, so he carried it because the team needed it, not because he wanted it. He could have pulled the "I'm a Corpsman" punk card and carried less, but that would have put it another one of us, and we were already maxed out.
He wasn't wirey at all. He actually enlisted as a Ship Firefighter, but lat-moved and became a Corpsman after two years (so he was in for six). He looked fat, but could move with the best of them. Never fell out of hikes, but couldn't run to save his life. He had to get selected to be in the Sniper platoon, he wasn't just assigned there.
Remember, you're at the beginning of your career. Your ability ramps up with your conditioning gradually. When I started, a 15k hike with 55lbs (no ammo, no body armor) seemed like a death march. At the end of my career, I was moving 15k through the night with 125lbs and hardly breaking a sweat and still able to fight when I got where I was going.
If you do go green side, you'll have a huge learning curve to get over. You'll be treated worse, pushed harder, AND everyone will hate you because your a soft-unproven Doc who has to live up the legends that passed before you (or shit bag Docs people will never forget). You are held to a higher standard.
Respect is the ultimate commodity in the military. It's very hard to gain, but the principle is simple. The more you talk, even casually, the more respect decreases (even among your best friends). The more you let your results speak for you and remain humble, the more it will increase.
People will not trust you. You will have to earn the trust by doing your best to live up to impossible standards without talking about it. Even after you've gained the trust and begin dealing in respect, opening your mouth will cause it to disintegrate.