So let them join and get them into shape. I’m guessing that basic training/boot camp will do wonders for these people.
The current military services do not have the budget for military personnel required to spend and waste on recruits who are unlikely to meet and maintain the minimum standards of performance. The Army and Navy draftees in times past were paid very poorly and the military services enjoyed comparatively better budgets for the training of the recruits, so they had more latitude to spend time and money on physically conditioning most obese recruits.