It's a generally true idea, but they use it to draw wrong conclusions.  From a 1000 calorie slice of pizza, someone may be able to fully digest it and get all 1000 calories, and another might swallow it whole and only a tummy ache and 900 calories. The problem is that it isn't relevant to the point these dumb fats are trying to make. First off, you can't get MORE calories, only LESS. If this was their problem, they'd all be too skinny. It's just like baseline metabolic rates. People burn somewhere between 800 and 1200 calories a day just sitting still.  A 95lb chick has very different caloric requirements than a 200lb man.  A fat 200lb man needs far less calories than a fit muscular 200lb man.  None of that really matters unless you're a top performing athlete who needs to know their exact macro requirements. For losing weight, it's absurdly simple. Eat less, move more. You don't even have to do the moving part....