What Is Leptin?
Leptin is a hormone – a chemical messenger that helps different body parts work together. Leptin sends a signal to your brain that helps you feel full and less interested in food. You may hear it called a satiety hormone. (Satiety means hunger feels satisfied.) It also plays a role in how your body turns fat into energy.
You’ve always got leptin in your body. It’s mostly made by your fat cells. But your stomach releases some when you eat. It circulates in your bloodstream and travels to your brain.
And that’s where leptin delivers a very important message: We have enough fuel!
Low levels of leptin, on the other hand, are part of the complex hormonal dance that makes you feel hungrier.
How Does Leptin Work?
Leptin is an appetite suppressant. When everything works the right way, it helps you maintain a healthy weight by balancing the amount of food you eat with how much fat you have.
More specifically, high leptin levels tell your brain “your fat cells are full,” which makes you less hungry.
If you’ve ever been on a diet, you might have noticed that you get hungrier when you cut your calories or start to lose weight. That’s in part because typically, your body automatically makes less leptin when you lose fat mass. Though, keep in mind that you never lose fat cells. They just get smaller.
But it’s not always about body fat. Simply fasting for several hours can cause your leptin levels to drop.
And hormones aren’t the only thing that affect hunger. There are deep-seated social and psychological issues that can change the cycle of hunger and satiety.
Even your regular lifestyle habits of diet, exercise, and stress management can play a part.
Do Certain Foods Boost Leptin?
Not really. You don’t get usable leptin from food, and there’s no evidence that specific foods help boost the hormone.
But a poor diet or extra pounds may make the hormone less effective (leptin resistance).
A healthy, balanced diet and regular exercise may help keep this problem at bay.
What Is Leptin Resistance?
Sometimes your brain tells you to eat more, even when you have plenty of leptin and lots of fat cells. That’s called leptin resistance. Doctors don’t test for it regularly, but experts agree it’s common in people with obesity.
Think of leptin resistance like insulin resistance in type 2 diabetes. That’s when the pancreas makes a lot of insulin, but the body doesn’t respond to it. Leptin resistance can lead to overeating and excess fat storage.
Other health problems can mess with your leptin signaling too. For example, chronic inflammation and high levels of triglycerides (a kind of fat found in your blood) can make it harder for leptin to cross the blood-brain barrier.
There’s ongoing research on “leptin sensitizers” to help improve response to leptin.
You can target insulin resistance, which often occurs alongside leptin resistance. Improve your sensitivity to insulin with medication, a healthy diet, plenty of exercise, and good sleep habits, and your leptin resistance may improve as well.
How Does Sleep Affect Leptin Levels?
Most humans have a “diurnal” rhythm to their day. That means they are active during the day and sleep at night. Leptin levels tend to peak between midnight and dawn, making you less hungry. That makes sense because there’s not much you can do about being hungry when you’re asleep in the middle of the night.
But sleep still plays a big part in leptin levels. A lack of shut-eye will disrupt all your hormones, including leptin.
It could make you feel hungrier because your brain sees a lack of sleep as a loss of energy that needs to be replaced.
And the reverse may be true as well. Being very hungry at bedtime can cause lower leptin levels, and that could interfere with your sleep. In fact, a lack of sleep can be a sign of starvation in people with a serious lack of body fat or daily calories.
Are Some People Leptin-Deficient?
There was a lot of buzz around leptin when scientists discovered it in the mid-1990s.
They had good reason to think leptin might work as a weight loss tool. It all started with a mouse.
For decades, scientists were curious as to why a certain breed of mouse kept overeating, lying around, and gaining weight. They eventually discovered the hormone leptin – and found that it played a big part in making mice feel hungry or full. This particular breed of weight-gaining mouse had a genetic anomaly that kept leptin levels low and hunger levels high.
Scientists thought people with obesity might be like that leptin-lacking mouse. But it turns out leptin deficiency is extremely rare in humans. Scientists know of only about 100 people in the world who make little or no leptin.
People with this extremely rare condition need daily shots of a leptin-like protein to control their weight, starting in childhood.
But when you give this same treatment to people who have the far more common condition of leptin resistance, it doesn’t change a thing. Doctors continue to work on the problem.
Do ‘Leptin Supplements’ Work?
Leptin isn’t a vitamin or mineral. You can’t absorb it from a pill. In fact, “leptin supplements” don’t contain any actual leptin. If they did, your stomach would simply digest it before it could have any effect on your body.
So what’s in them? All kinds of stuff.
Some contain caffeine, which may suppress your appetite. Others are just a mix of herbs and vitamins. They might not be harmful, but there’s no evidence they’ll have any effect on your leptin levels.
Ask your doctor before you take any supplements, especially if you also take prescription or over-the-counter medications.
What Else Does Leptin Do?
Though scientists have just scratched the surface when it comes to leptin, they know it plays a part in various aspects of bodily health. That includes any function that requires energy.
For example, if your leptin levels are too low, the immune system won’t switch on fully. In addition, healthy leptin levels can boost your chances of getting pregnant or carrying a child. It sends a signal to your brain that it’s OK to ovulate and prepare the uterus for a baby.
This makes sense, because a body needs plenty of energy and nutrients to support a growing baby. During pregnancy, leptin can help babies get the right nutrients to grow. But this may not work properly in women with obesity.
Can High Leptin Levels Cause Problems?
Leptin gives a kind of green light signal to many other systems in the body. That includes your immune cells. A strong immune response is a good thing when you’re sick. But too much inflammation can cause health problems.
People who have obesity and high leptin often have chronic inflammation. That’s linked to heart issues, cardiovascular diseases, insulin resistance, and cancer.
In women, high leptin and obesity can boost the chances of breast cancer. Leptin-related inflammatory “cytokines” send signals that seem to impact how breast cancer cells grow and stay alive.
It’s important to note that not everyone with obesity will develop breast cancer. But in those who do, leptin can promote cancer growth.