This is what is called the 'Starvation Metabolism' response, where the body, when deprived of adequate calories, will adapt to need fewer calories to function. As a result, dieters often regain the weight they lose almost immediately because they have starved their body into becoming a "fat-storing machine." Sadly the truth! For most of its history, vientre plano de la noche ala mañana the human race was subject lock, stock and smoking barrel to the whims and fancies of dear old Mother Nature, especially where our nutritional needs were concerned. When the conditions were right, food was plentiful; when they were not, the populace starved. As a result, evolution shaped our progenerators bodies in such a way that during times of plenty, they were able to pack on layers of fat to provide them with the sustenance they needed to get through the lean times...not the 'fit' times, the 'LEAN' times!