Yup.
Exercise spikes his hunger, especially lifting heavy weights.
Damn near impossible for him to not have a big meal after a workout. Even if its a healthy meal its far more calories than what he'd burn in a workout.
Basically he wants to be more 'cut.'
To weigh less (15% of his body weight lighter), with a smaller body fat percentage (Under 10%), and I think for the muscle to be more defined... more apparent as opposed to be under a layer of fat.
Didn't put all this info in the OP because it would seem like information overload. He told me his plan and seems enthusiastic about it so I didn't want to discourage him, but he did mention he's looking for suggestions.
If he can’t control himself becoming fat then the problem isn’t the lifting. The higher probability here is that there is some psychological factor at play, or that he's trying to do too much too soon, and not giving himself time to adapt to new habits and for his appetite to adjust to a lower caloric intake.
If what he thinks was true, people who exercise a lot would be on average fatter than sedentary people, which is the opposite of what we commonly see. Some recreational and heavyweight powerlifters are fat, yes, but that's mainly because being heavier and gaining muscle mass at all costs is mostly an advantage when it comes to chasing numbers, and many just don't care about anything else. Lifters who have to restrict themselves to a weight class (of which there are many) are generally very jacked and strong compared to sedentary people.
So, it sounds like he's giving himself permission to eat excessively just because he thinks the lifting somehow justifies or requires it, so he will obviously gain weight. Or it's also probable that he tried to diet dramatically while lifting very hard, so of course that will make him feel like shit. He could do the dramatic dieting if he wanted, and he will lose weight, but it doesn't sound like something that would work for him, if it requires stopping all training. He could start by modestly cutting maybe 10% of his caloric intake or something like that, tracking what he eats, waiting a few weeks more, cutting some calories again, wait for his appetite to adjust until he feels settled into the new diet, replacing low-satiety-high-calorie foods for high-satiety-low-calorie ones, waiting a bit, maintaining the new weight for a couple weeks, then cutting a bit more, and so on. There's many ways to do it, and he should look to satisfy cravings with low calorie snacks, which requires some planning. All of that could be done without modifying the training significantly, and without crash-dieting, although PRs may not come by as easily. If he likes eating large meals after training, maybe look for ways to make this large meal less calorically dense, while still letting it be larger, and cut calories from other meals during the day.
With his logic, why wouldn't his appetite become what it is now again after he starts lifting heavy again, and what would stop him from becoming fat again when he tries to gain back the muscle? Doesn't make sense to me. Sounds like a recipe to lose a bunch of hard earned strength and muscle for no good reason.