a lot of energy (calories) to break down, absorb, and use inside of the body. some of these foods contain very few overall calories and, therefore, may actually force the body to call upon its energy stores – in the form of stored glucose and fat – to finish ‘processing’ the food.
obviously, any diet that involves eating only these types of foods (such as the very popular negative calorie foods diet) will certainly lead to both quick and long-term weight loss. but, in reality, it may be difficult for many people to eat only negative calorie foods for more than a couple of weeks. basically, even though these foods are 