There are healthier alternatives when eating on the run, some places have a more weight friendly menu now as well, Salads are always a good thing, just limit the amount of dressing, soup and sand where you can ask for little or no mayo etc on it, subs,
A lot of it has to do with how it is cooked, and what condiments it has with it, mustard instead of mayo, little to no dressing or dips, portion size is key in this, save some for later and drink water or something else that you can control the sugar in, it does help if you can get him on board with the cut backs, watching him eat to his hearts content doesn't help. but he has to want to do it or it won't work for him either, have other people as your support , it is important to have strong support, that will tell you if you slip and fall that you can get up and keep going. And take that time to do the 15 min walk, just that will make a difference.
I took a list of things that I could live with out and made the decision before hand not to eat them, then there is a list that I refuse to give up and just limit how much and how often I eat them, I gave up ketchup and still eat icecream,