I think a lot of the “hunger” is because unlike most Americans, no one is snacking. You’ll get three square meals a day (and if you’re eating MREs, they’re loaded with calories. You’ll be full…and constipated. )but you’re not going to be raiding the cabinets for some potato chips. Most people are accustomed to being able to do that, and think they’re starving, when really, they’re just getting the appropriate amount of calories instead of overeating.
Really, if I can wax philosophical for a second, the entire point of military training is to teach the person that they have more mental and physical strength than they think they do. The idea being that if they’re ever in an extreme situation, they’ll know they can push on despite being tired, or hungry, or cold, or afraid. That’s why in training they hit you like a ton of bricks early on. They want you to think, “Oh, man. I screwed up. I can’t do this. I’m not tough enough. I shouldn’t be here.” There’s a big sweaty man screaming in your ear that you’re the worst POS they’ve ever seen, and you believe him. (Even though you later realize he says that to everyone.)
Then you slowly come together as a team and start overcoming the obstacles they put before you. By the end, you’ve done all this stuff you never thought you could before. And that’s where the confidence comes in. He’ll know he’s capable and have the pride that comes with doing something difficult.