Originally Posted by
Philbert
Adam, The reason only fat calories are stored in almost all cases is because eating a caloric excess that is larger than your fat consumption is extremely difficult for any time span relevant to body composition. In the hypothetical of the couch potato above, if he ate 2,000 Cal above maintenance he would gain 4 lbs of body fat per week. The people I have seen gain fat quickly are usually more on the order of 1-2 lb per week, and then they keep doing it for a year. If he ate a 500 Calorie excess he would have to get his fat below 20% of calories in order to store any protein or carbohydrate as fat. A 20% fat diet is not appetizing enough to overeat more than 500 Calories a day on, outside severe psychopathology or severe determination to gain weight. Assuming he did somehow manage to overeat 1,000 Calories at 25% fat (considered a low fat diet)a large part of the 333 Calories of excess protein/carbs would be burned in the storage process, and by elevation of his metabolic rate. If he was really determined and ate the 4,000 Calories still at 25% fat he would store the 1,000 of fat, he would burn a few hundred of carbs, he would store some protein as higher levels of various enzyme, structural, or serum proteins, and he would convert some carbohydrates and/or amino acids to fat. After doing this for one or two days he would say: "at last, I have proved that other macronutrients are in fact stored as fat" then he would go back to eating 500 over maintenance or switch to a higher fat diet because what he was doing was disgusting to him. Try it for three days. To demonstrate the fact you need a month or so of MyfitnessPal or equivalent data along with weight so you actually know what maintenance is, then adjust protein/carbs to maintenance plus 1,000. See how long you can keep it up, and report back.