What I always wondered about eating healthy is, is it the unhealthy foods on their own that is the root cause, or the fact that unhealthy eaters don't eat whole

What I always wondered about eating healthy is, is it the unhealthy foods on their own that is the root cause, or the fact that unhealthy eaters don't eat wholesome foods? For example, if I eat McDonalds, but then I also eat a bunch of fruits and veggies, would that mitigate the risk?