Her metabolism is definitely keeping her in check. If she gets some good running in once a week, we're in good shape. Otherwise we mostly just do leashed walks (and they're not super long) or some days we do nothing at all. She could easily be fat and probably would be if she were another breed. One thing I've noticed with boxers, is that I've never seen a FAT one. The sedentary ones have poor muscling but their weight in general typically stays okay.
Honestly I don't even know how I came up with 3 cups for her lol. Because I don't think any bag of food ever recommended it. She just loves to eat and anything less than that doesn't look like much food! She got 2.5 cups today and doesn't appear starved lol. We'll stick with this a while and see where it takes us!