It is important to understand glycogen stores and weight loss. Here’s a great paper on the subject (The American Journal of Clinical Nutrition, Volume 56, Issue 1, 1 July 1992, Pages 292S–293S. Glycogen storage: illusions of easy weight loss, excessive weight regain, and distortions in estimates of body composition. S N Kreitzman, A Y Coxon, K F Szaz).
Glycogen is stored in the liver, muscles, and fat cells in hydrated form (three to four parts water) associated with potassium (0.45 mmol K/g glycogen). Total body potassium (TBK) changes early in very-low-calorie diets (VLCDs) primarily reflect glycogen storage. Potassium released from glycogen can distort estimates of body composition during dieting. TBK changes due to glycogen mobilization were measured in 11 subjects after 4 d dieting with a VLCD. The influence of water-laden glycogen on weight fluctuations during the dieting process, the exaggerated regain if carbohydrate loading occurs, and the implications for weight control programs and overestimation of nitrogen losses with dieting are discussed.
The paper points out that the energy deficit required to reduce weight with glycogen as fuel is 1800 calories/lb which is less than the 3500 calories/lb for fat.