Diets where you severely limit your caloric intake simple do not work for long term weight loss for several reasons the most important being the resulting loss of muscle caused by such a diet. Whenever you starve yourself you will lose weight in the short term but unfortunately a large percentage of the weight will be muscle. Whenever you lose muscle you reduce your metabolism which is the worst possible thing you can do when you are trying to lose weight and keep it off because metabolism is what causes you to burn calories for fuel all the time. People that go on starvation diets usually end up gaining weight in the long term because as soon as they start eating normal again they gain weight because they have a lower metabolism from the loss of muscle meaning a lower demand for energy so the diet that once kept them at the same weight now provides more calories than their body needs each day so they gain weight. The same people get even more desperate and starve themselves even more which causes even more muscle to be lost which ultimately results in an even greater weight gain in the long term. It is a viscous cycle that is commonly referred to as yo-yo dieting because of the way people go down and up and down an up and never lose any real weight. If you are serious about losing weight the right way then learn to never starve yourself to lose weight but rather employ a good healthy diet along with proper exercise and the right nutritional supplements and you will easily achieve all of your weight loss goals.