12 lbs = 5450 g. 500 g of that could be glycogen, stored along with 1500 g of water. That's 2000 Calories and 2000 g in total. If the remaining 3450 g is fat

12 lbs = 5450 g. 500 g of that could be glycogen, stored along with 1500 g of water. That's 2000 Calories and 2000 g in total. If the remaining 3450 g is fat, it would be 31000 Calories, for a total of 33000 Calories, or 4700 Calories/day over the week. Not a reasonable amount! Taking your 2500 Calorie/day value, I get about 1700 g of unexplained weight loss.