I feel you. Every human being is in constant pursuit of pleasure or happiness, there not only nothing wrong with that, there is pretty much the only possible state to be in. When "complex" sources of pleasure, such as meaningful relationships or achieving your goals, either become unattainable, or devalued because of a shift in the worldview, we all switch to simple instant gratification, and I know it's not much of a consolation, but at least junk food isn't the worst thing to be addicted to. If you're depressed and experience anhedonia, the physical sources of pleasure are usually "the last to go" as well, you might lose your ability to enjoy anything else, but you will still like eating and sleeping. I wish I could offer you a simple solution to this problem, but I don't have one. One thing I do know from my own experience and experience of other people is that you're unlikely to constantly feel like grazing on something when you feel genuinely entertained or invested into any activity. But I do realize that finding things that are entertaining or engaging can be very hard.