Lifestyle tips

It depends on the circumstances. If they are actively pursuing a goal and you are actively sabotaging your them against their will, that’s not being a good friend. But if that is just the lifestyle you two have, and they are happy, content, neutral or otherwise don’t care, then you are not doing anything wrong. They have the free will to accept or refuse what you offer and the environment you create. If they have an issue with something, they can bring it up. They are your friend and you care about them. If you were truly doing something wrong, you’d know it. You’d probably never do it in the first place.

If you feel that guilty, get some healthy items along with your usual stuff. Not a whole lot of it - just enough for him. If he eats it, great. You now have a system where you can be a pig without it effective him. If he doesn't it eat, you can sleep well knowing that it's his choice.

How does she feel about it? Does she know about your gaining?

Getting healthy options is a good idea. Personally, I would encourage my roommate/friend to buy their own food. Say it’s about money or whatever.