https://www.military.com/join-armed-forces/disqualifiers-med...
Honestly Basic training with a food allergy, sounds like hell. You're pretty much starving for a month, and you don't get the luxury of choice while eating.
I was a smaller guy when I went through in 2009, and I was required to eat every last thing. I can now eat 3 full meals in less than 2 minutes. But I feel bad for someone who's got an gluten intolerance, because a DS isn't going to take that as an excuse.
No, even when there's a draft they don't accept people with certain medical problems. Someone who requires special meals to get enough calories to do his job would more than likely tax military logistics more than his labor is worth while deployed.
Edit: I guess people don't like the above idea, but it's true:
http://aaugusti.umwblogs.org/hist-375-military-history/#_ftn...
> Michael was a young man during the era of the Vietnam War. He was given the lottery draft number nine and had to get a physical to proceed with the draft process. Michael attempted to use an allergy to wool as an excuse to get out of the draft. He was told to wear wool socks to see if the allergy was true. Under the socks, Michael used a solvent to create a rash to the wool. He tried several times before an Army doctor issued him as medically ineligible for service.
https://www.nytimes.com/2007/02/14/us/14military.html
The effect on the army is unclear. Note that even during the surge more than ninety percent of recruits required no waivers. So you can spin the story as the number of recruits with clean records dropped from 98% to 96% which doesn't matter, or its a crisis that the number of troublemakers doubled.
This is a personal ancidote from my experience only, but it was generally understood that during the Iraq period circa 2003 If you have a pulse, you were qualified to enlist.
https://www.reddit.com/r/army/comments/9gl5vt/celiac_disease...