THE LEPTIN SPIRAL
Leptin is stored in and secreted by fat cells. As you gain more fat mass, leptin levels increase to tell your brain to eat less and burn more calories. Conversely, if you cut down your calories and start to lose body fat, leptin levels go down, which then sends a signal to your brain to eat more and burn less! Think of this conundrum as a safety mechanism that regulates energy expenditure and food intake.3
Based on this information, you would think someone carrying around extra body fat would have more leptin, and thus, fewer desires to overindulge in food. This sounds great in theory, but research has shown that despite an elevation in leptin levels, obese individuals continue to overeat and energy expenditure fails to increase significantly.
This is called leptin-resistance. As someone gains weight, the signal to their brain can get “disrupted” or become less “sensitive,” which causes them to continually overeat.