This discouragement is based on the flaw of thinking that they must be losing weight in order to change their body composition. These individuals often forget. But seeing the scale flash three pounds less than last week doesnt necessarily mean all your hardwork is paying off. Theres three explanations for weight loss, says strength and performance specialist Joel Seedman, Ph.D., owner of Advanced Human Performance in Atlanta Losing fat, losing muscle, and losing water. This is why you lose so much weight on a diet like Atkins the first 2 weeks its mostly water. Of course, increasing your carb intake will make you gain weight again water retention. Muscle Gains Fat Loss. Youll gain muscle while losing fat when you get into strength training. Though most people use the terms weight loss and fat loss interchangeably, they are not in fact the same, and require different methods to.