How good (or useful) a food is to a particular goal is all relative to what you might be eating if you weren’t eating that particular food?
For example, “Are granola bars a good food for weight loss?” Well, if it’s replacing a Snickers Bar, then yes, it’s a good food to sub in compared to the alternative. But if you’re eating the granola bar as a way to justify skipping a salad topped with grilled chicken, then the granola bar is a far inferior option.
This applies to portions as well. When it comes to weight loss, two granola bars in the same sitting are worse than one granola bar. One granola bar is worse than half a granola bar. And (provided you’re not eating something else in its place) zero granola bars is going to be more conducive to weight loss than the half a granola bar.
So next time you see a food touted as being super healthy or great for weight loss, remember that that’s always a context-based description. Ask yourself what you would be eating instead if you weren’t eating that, or how much and how often do you intend to eat it. Keeping this in mind, there are no purely good foods, nor are any purely bad.
Let’s dismiss nutritional duality.