system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What actually makes a food healthy/unhealthy? Are all processed foods automatically “unhealthy”?

Obviously low-calorie and low-carb are different than “healthy”, but they are much easier to identify when reading a nutritional label. What should someone be looking out for to still eat (relatively) healthy without only eating raw veggies?
gpt
I wouldn't think of any single item being healthy / unhealthy. (Besides obvious candidates like empty calories such as certain sweets)

Think about what you are eating as a whole. The best diet is the one that 

a) gets you the calories that you need including those you'll burn

b) gets you all the recommended nutrients

c) doesn't give you excessive amounts of anything.

d) obviously as little as possible downright harmful substances like alcohol

Wether you get there by eating mostly vegetables or yoghurt, frankly doesn't matter.