Why do diets fail? Remember this, and remember this well: your mind and body are one. In other words, once your body figures out that there's less food going around, your body will start to slow it's metabolism down and hold on to as many calories as it can. Your mind on the other hand, realizes this and starts gearing to finding more food. You will think about food all day long and eventually you might even give in and binge. Then you'd feel terrible.