Reboot Your Hormones, Pt 2 (3:55)
What is leptin and how does it work?
Leptin is a hormone that plays a crucial role in appetite and weight control. It is thought to have at least two major functions. First, it crosses the blood-brain barrier and binds to receptors in the appetite center in the brain, regulating brain cells that tell you how much to eat. Second, it increases sympathetic nervous system activity, which stimulates fatty tissue to burn energy.
What is leptin resistance?
Studies in mice have shown that giving animals leptin reduces overeating and obesity. However, many obese humans have been shown to have high amounts of leptin circulating in the blood, but it doesn't seem to affect appetite or energy expenditure. This is termed "leptin resistance," because even though the body has more than enough leptin in it, it doesn't respond to it the way it's supposed to.
Why does leptin resistance happen?
While the definitive cause of leptin resistance isn't known, there are two main hypotheses. The first is that leptin in the blood is for some reason not reaching the right targets to control appetite. The second is that the receptors that leptin binds to stop functioning properly to tell the cells to respond to the hormone. This commonly happens in overweight and obese people, and makes it even harder for them to control appetite and weight gain.