Correct me if I am wrong, but what you are saying is that it is relative to overall diet. So if I eat nothing but candy bars and cokes, than eating pizza and gatorade is essentially healthy because it is better than the diet of candy bars and soda? If that is what you are saying then I think that is a bit ridiculous.
Food definitely is healthy or not healthy. A candy bar doesn't become healthy because it is relative to something else. It is unhealthy period. Health is not a relative thing.
I get what you are saying if you mean that something can be healthier in a relation to another option. For example, someone who only eats mcdonald's and then steps it up to Subway is making a healthier decision. However, that still doesn't make the subway healthy because it is better than mcdonalds. At the end of the day they are both crap. One just isn't quite as ****ty as the other.
A solid turd is better than projectile runs from and upset stomach. But at the end of the day, they are both still ****