I think the point was that you feed a foodstuff to few different people and each one will derive different caloric and macro nutrient value out of it. Let's say

I think the point was that you feed a foodstuff to few different people and each one will derive different caloric and macro nutrient value out of it. Let's say there are two different diets, both provide strictly less calories than you use. One of the diets works well with your metabolism and biochemical processes to give you energy and keep you sated. Second diet makes you feel constantly hungry and apathetic. So, yes, you will not lose weight if you consume more calories than you spend, but bare calorie count is not sufficient to quantify the diet.