&gt; It you a eat a lot of fat you will get fat too. Its all about moderation. If you eat 4000 calories of FAT everyday you will get fat<p>Calories-in-calories-out without considering the hormones that drive both satiety and crucially fat-storage-vs-fat-mobilization (and thus drive both how many calories are craved and how many are burned) is misguided. CICO isn&#x27;t wrong, but for all practical purposes what drives CICO in real life are those hormones, which are in turn affected by the ratio of fats and carbs in diet: chiefly insulin and leptin. How those are affected by 4000kcal-of-carbs-low-fat (badly) vs 4000kcal-of-fat-no-carbs (benign&#x2F;beneficially) is easy to find out.<p>4000kcal of fat and low carbs, if one could stomach it for years, after a few weeks of keto-adaptation? They&#x27;d be a tad little bit fatter than they&#x27;d like, and feel profusely hot and sweaty. As their leptin and insulin sensitivity gets ever-better, 4000kcal will soon become impossible to stomach, however. 4000kcal of carbs and low fat for years, just become obese and get metabolic syndrome.