The hypothalamus integrates incoming signals regarding energy intake and expenditure. However, the control mechanism was still unknown. Romaine Hervey proposed in 1959 that the fat cells produced a circulating “satiety factor.”12 As fat stores increased, the level of this factor would also increase. This factor circulated through the blood to the hypothalamus, causing the brain to send out signals to reduce appetite or increase metabolism, thereby reducing fat stores back to normal. In this way, the body protected itself from being overweight. The race to find this satiety factor was on.
