I can tell you what would happen.
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In the first couple of days, you would likely lose a great deal of weight. The amount depends a little on how much salt and fluids you take in because those first couple of days will be your body dumping water and glycogen. This weight is pretty much phantom weight because if you eat carbs, you will regain it extremely quickly. This is why a lot of people see huge stalls in weight loss if they “cheat” on their low-carb diets. Carbohydrates will cause glycogen stores to increase and will cause water retention.
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The first couple of days you will likely feel pretty wretched. Hungry, restless, possibly nauseated, possibly headachey. You will probably be willing to kill your mother for a cookie.
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By day 4 or 5, eating that many calories will gross you out. You won’t be very hungry and if you tracked what you were consuming willingly, it’d probably be closer to 1200 calories than 3000. You may still be having intense sugar cravings, though these should taper off soon. You may find that you are incredibly constipated and your breath stinks. You may feel irritable and without a ton of energy. You may feel great. This seems to be pretty individual.
And what happens next seems to depend on the person. I have never tried to force myself to overeat (eat past the point of satiation) on a low-carb plan, and I’m pretty sure that would have proved disastrous for me. If I went on this test-plan, I would gain weight since I wouldn’t have the initial water/glycogen drop (and I have and do count calories. I know exactly how much I’m eating and what it takes to lose, maintain, and gain weight).