How much body fat you have is regulated by a complex and powerful hormonal system that ensures you don’t lose energy stores for survival purposes and that you don’t store excessive amounts of fat. These hormones interact with each other and the hypothalamus, the master of the brain that regulates appetite, food choices, emotions, and your biological clock. In normal circumstances, your hormonal system works at keeping your body fat mass pretty constant within a reasonable “normal” range. In addition to regulating appetite and your caloric intake, these hormones regulate how much fat you will burn on a regular basis even when doing nothing (Basal Metabolic Rate). When you become overweight or obese, your metabolism (Basal Metabolic Rate) automatically slows down.The major hormonal players are: Leptin - A hormone produced by fat tissues that works on suppressing appetite, speeding up metabolism, and accelerating fat burn in the mitochondria. Thyroid Hormone - The touchstone of metabolism. It also activates mitochondria to burn fat and generate heat. Growth Hormone - Has the ability to break down fat. Insulin - An executive hormone that balances energy in the body and primarily acts on liver, muscle, and fat tissues. Insulin resistance or inefficiency often results in a self-perpetuating cycle of fat storage and inflammation that leads to metabolic syndrome and diabetes. Ghrelin - A hormone predominantly produced by the stomach. It stimulates appetite, increases cravings, and slows down metabolism and fat burn in the mitochondria. Cortisol - An important hormone produced by the adrenal glands that affects food choices, appetite, and body fat distribution. Excessive cortisol causes fat to shift to the abdominal area and counteracts the effects of both fat burning hormones, leptin and thyroid hormone.