We have to do it. Some of us have to do it in different ways. Doing small things where you can is all well and good but literally none of us are making a single impact in capitalism by making different choices about how we're forced to participate in it. Focus on tearing it down together rather than picking apart individual choices because those individual choices still result in participating in capitalism.
I have never heard a vegan say this. If you want to lose weight on a vegan diet, you can. If you don't want to lose weight, you don't have to. If you're eating a metric fuckton of cheese and fatty meats I mean yeah, maybe.