I never noticed before if people were looking at what I was eating.
Now, though, coworkers comment ALL THE TIME about my lunch/snacks, especially if it's a new situation.
I worked with a wonderful group of women this summer and they were all primarily southern and were just fascinated with what I was eating (homemade salad "kits", plan avocado, sliced veggies). They just weren't used to seeing someone eat like that. But they were never rude, just inquisitive. And the remarks never bothered me anyway.
Now I just work with a bunch of boys and they are health nuts too, or just don't notice anything not right in front of them
Perhaps you are just self conscious, or perhaps they are just being rude. Either way, it's none of their concern. Just keep doing what you are doing (easier said than done, I know).