Whoever buys the food has a great deal of control over what will fill him up or make him hungry. So stock up on complex carbs, fruits, veggies, and protein (eggs, various cheeses, nuts, lean meat, tuna, etc). Things like juice and tonic (soda) probably shouldn't even be in the house. As for junk, it's amazing how many forms it comes in... crackers, most cereals, frozen breakfast sandwiches or waffles, cookies, chips, granola bars, yoghurt with fruit or flavoring, candy, fruit roll-ups, ugh!!! Each of these items end up making a person hungry again quickly. It's a real problem for children. Honest story: when the kids were little I only had one box of cookies a week. When they were gone, they were gone.
Also, food that is crunchy or chewy tends to make us work harder to eat it and ends up making us feel fuller. I'm thinking of popcorn, raw veggies, unsalted nuts.
And food that is eaten with a fork takes longer to eat and is more likely to satisfy. So hot dogs, hamburgers and sandwiches can be scarfed down and you could still be hungry. But whole wheat spaghetti with hamburger takes forking time and lots of chewing. Hot dogs and beans take time. And of course, the give and take of conversation really helps. So snacks and meals only at the table and only with someone else's company is ideal. Even if you only sit with him for a few minutes while he snacks. Food on the run does not compute in the mind that he has eaten.
Well, best of luck! Whatever you do, please don't talk to him about food and his intake, unless weight is a critical issue. And then talk to a nutritionist about the best way to address this. Boys get body image issues and food control issues, just as girls do.