Why leptin is the most important hormone for metabolic health.

Leptin was only discovered in 1994, but we are soon learning that it is the most important hormone when it comes to metabolic health. Leptin is released by adipose (fat) cells and when it’s working properly it helps regulate how much stored energy (fat and glycogen) your body stores or burns. It does this by providing nightly “downloads” to the hypothalamus in the brain letting it know how much stored energy is available in the body.

Let’s say for example that you’ve gained a few pounds recently. Leptin would signal your brain to reduce your appetite, increase energy expenditure (breaking down your stored fat and glycogen) and inhibit fatty acid synthesis (fatty acids get stored as triglycerides). It also increases insulin sensitivity helping your body utilize glucose better.

Unfortunately, similar to insulin resistance, you can develop leptin resistance. If you have insulin resistance, you likely have leptin resistance. The more adipose (fat) cells you have, the more leptin you have. Eventually, the cells become less responsive to leptin leading to overeating, weight loss resistance, and increased storage of fat. Leptin resistance is associated with obesity and hyperlipidemia (high cholesterol and triglycerides), fatty liver, insulin resistance, and Type 2 Diabetes.

Obviously, diet plays a huge role in developing leptin resistance. When you eat too many carbohydrates your body will store them as fat. Remember you want your body to be metabolically flexible and able to easily flip the switch between burning fat or glucose as fuel. Regulating blood sugar is extremely important. Even if you are eating “healthy” carbohydrates you can have blood sugar dysregulation.

Your circadian rhythm also plays a significant role in leptin signaling. If you are not getting out in the morning, especially during UVA rise, you are missing signaling from the light that releases leptin from adipose cells and activates a pathway that helps maintain blood sugar and supports metabolic health.

Next time you are at the doctor I highly recommend having your leptin tested. The optimal range is between 4-10 ng/mL. I think it's one of the most important lab markers for metabolic health.

Resource: DOI: 10.5772/intechopen.112499