Leptin: How Does This Fat Burning Hormone Work?

4 Minute Read

Your hormones play a HUGE role in your hunger levels and how/when your body will burn fat vs sugar. When your hormones are not balanced properly, it makes it so tough on your body to lose weight because you are starving and your body only wants to burn sugar! Leptin is an important hormone that plays a part in your hunger levels and how your body expends its energy.

What is Leptin?

Leptin is a hormone that is actually made by your fat cells. Leptin wasn’t discovered until 1995 and it was originally thought that the only function of fat cells was to hold fat. As we have discovered, your fat cells play a VERY active role in the body. Now we know how much of an influence fat cells have over the brain!

What does Leptin do?

Leptin Function

Your fat cells or adipocytes make leptin and release it into the blood. Leptin travels to the brain and attaches to its receptors in the hypothalamus.

The hypothalamus will then send out signals to adjust hunger levels AND energy usage in the body.

So, leptin will:

Decrease appetite - Your fat cells send a signal to the brain that you have enough fat and it’s time to stop eating. So, leptin will suppress your appetite.

Increase energy expenditure - As leptin increases, it is telling the brain that there is too much fat and the body needs to increase energy use to decrease fat amounts.

If a person is overweight, they will have high leptin levels and vice versa, a person with a low body weight will have low leptin levels.

Sounds like an amazing hormone that should decrease hunger and increase caloric expenditure if you gain fat, right? So, why do you feel hunger when you gain fat? Leptin Resistance!

What is Leptin Resistance?

Leptin Resistance

Leptin is a hormone made by your fat cells that decreases hunger AND increases energy usage in the body. So, when the body has too much fat, it should be signaling the body ways to lower fat levels!

Sounds great, but we don’t see that happen. So, what goes wrong?

In short, your brain becomes resistant to leptin. So, even though the signal is there, the brain can’t “see” it!

The brain isn’t receiving the message that there is plenty of fat on the body, so the brain thinks you are starving. So, guess what! That means more hunger and a decreased metabolism for you.

Your brain thinks that you are starving when you are leptin resistant!

The body ends up in this cycle of leptin resistance - the fat cells are making leptin (arrow) the brain doesn’t get the message (arrow) so the brain increases appetite and decreases energy usage (arrow) you eat more (arrow) increase fat storage.

What Causes Leptin Resistance?

Leptin resistance is a real problem if you are trying to lose weight.

So, what causes leptin resistance? Basically, anything that causes inflammation can cause leptin resistance.

Poor nutrition

Not eating the right foods for your body will throw off ALL hormones. You may also be missing essential nutrients needed to break fat down. You may be eating way too many calories. You may be sensitive to specific foods that you are eating. Having the right nutrition plan for YOUR body is so important to decrease an inflammatory response.

Insulin resistance

Insulin and leptin resistance usually go hand in hand. So, if you are struggling with insulin resistance, you are also likely leptin resistant.


Lack of sleep is a stressor that will also disrupt hormone signaling.


Stress of all types, like mental, emotional, and physical, can also negatively affect your hormones. Remember, your body works in conjunction with all organ systems at the same time.
So, any stress that is affecting one area of your body will affect ALL areas of the body.


Toxins will create stress in the body by causing damage to tissues. Toxins can come from your food, household cleaners, beauty products, or anything else from the environment that you ingest, breathe in, or put onto your skin.

As you work on your health, making these small changes will affect so many hormones, including leptin!

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