Yep. Bioavailability and uptake are real things. Depending on your gut bacteria, natural enzyme levels, etc. you may not be able to fully digest and absorb 100% of the calories from 1000 calories worth of veggies before they pass through your digestive tract. I guaran-fucking-tee anyone's digestive system will be able to fully digest and absorb 100% of the calories from 1000 calories worth of simple fast-digesting sugars.