Bodyfat is a storage medium. There are time delays, which complicate energy balance and weight loss in practice. Also, some calorie-deficient diets result in

Bodyfat is a storage medium. There are time delays, which complicate energy balance and weight loss in practice. Also, some calorie-deficient diets result in a higher average degree of hunger than others with equal caloric input. Some high carb diets produce insulin spikes and subsequent hypoglycemia and hunger pangs. And some calorie-deficient diets result in different muscle/fat loss ratios than others. Finally, not all exercise activities have the same effect on body composition. Long slow distance promotes a lean body, but it's not for everyone.