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Why is it that two people can eat the same thing and respond differently? One person may feel full while the other is still hungry. Another might burn off calories quickly while the other doesn’t.
It turns out there is more to appetite and weight than just what you eat and how much you exercise. Hormones like leptin are one important part of the process, too.
What is leptin?
Leptin is a hormone that helps regulate appetite, metabolism, parts of the immune system, and more. It’s produced in the body by a type of fat tissue called white adipose tissue.
Sometimes leptin is called a fullness hormone. That’s because it helps control how many calories you take in and how many you burn (otherwise known as your energy balance) (Dornbush, 2021).
How does leptin work in the body?
After you’ve consumed enough calories during a meal, your fat cells release leptin. Leptin binds to a leptin receptor protein, which sends signals that you’re full to the brain or central nervous system. This feeling of fullness (satiety) signals you to stop eating and burn off more calories.
Your body uses fat cells called adipocytes as fuel, and when you’re well-fed, leptin signals your body to burn off this fuel. During periods of starvation, you don’t have enough calories or body fat stored up. This makes your levels of leptin drop, signaling your body to eat more and store calories for energy instead of burning them off (Dornbush, 2021).
Leptin and ghrelin
The hormone leptin doesn’t regulate appetite all by itself. It works hand in hand with another hormone called ghrelin. Ghrelin is an appetite hormone that tells you when to eat and store calories. Your appetite and weight are strongly influenced by the balance between leptin and ghrelin.
For example, leptin levels decrease to save calories during starvation while ghrelin levels increase. This indicates that you’re hungry and need to eat more. When you’re well-fed, the reverse happens (Klok, 2007).
Set point theory may explain why you aren’t losing weight
Does leptin affect weight?
It can. Eating triggers fat cells to release leptin, which leaves you feeling full and encourages your metabolism to burn more calories. This complex and fascinating system is set up to prevent overeating and excess weight gain (Dalamaga, 2013).
Leptin is made in adipose or fat tissue. The more adipose you have, the more leptin you make (Park, 2015). You would think that producing more leptin means losing more weight, but that’s not necessarily the case.
People with obesity have more adipose and typically very high leptin levels but can still have difficulty losing weight because of a condition called leptin resistance (Considine, 1996).
What is leptin resistance?
Leptin resistance occurs when the brain can’t receive or respond to the signals leptin sends out. Fat tissue still accumulates and produces leptin with leptin resistance––the catch is your brain doesn’t register that you’re full.
Since you still feel hungry, you continue eating and building fat tissue. Your body doesn’t respond to leptin signals to burn off calories, so you’re basically eating more without burning anything off, which can result in weight gain (Myers, 2012).
Leptin resistance may be congenital (meaning you’re born with it) or be caused by inflammation in a part of the brain called the hypothalamus (Thaler, 2012).
It may also come from excess fatty acids, a component of fats. Like the ones in saturated fats, some fatty acids can block the brain’s response to leptin and trigger resistance (Kleinridders, 2009).
How does ashwagandha help with weight loss?
Leptin for obesity treatment
Since leptin makes you feel full and burns calories, it seems logical that you could use it to treat obesity. However, studies have shown that giving people leptin doesn’t help (Paz-Filho, 2011).
This is because people with obesity already produce leptin. In fact, since they have more fat tissue, they usually have higher than average leptin levels, so adding more isn’t helpful (Maffei, 1995).
There’s one exception to this. Some individuals have congenital leptin deficiency (CLD), meaning they were born with almost no leptin at all (Sáinz, 2015). People with CLD may have obesity and are at risk for complications like high cholesterol, cardiovascular disease, and type 2 diabetes.
People with CLD are sensitive to the effects of leptin but don’t have enough of the hormone. When they’re treated with leptin, it basically replaces a missing part. In this circumstance, leptin treatment helps reduce weight, lower cholesterol, and balance blood sugar (Paz-Filho, 2011).
Leptin deficiency is much less common than leptin resistance, so this treatment isn’t helpful for everyone (Vatier, 2012).
Should I take leptin supplements?
Ironically, leptin supplements aren’t actually leptin. Also called leptin resistance pills, these supplements contain ingredients like vitamins and extracts that claim to increase leptin sensitivity in people who are resistant (Sáinz, 2015).
There’s evidence that some of the ingredients (like linoleic acid and green tea) slightly affect leptin levels, but there’s no proof these help with appetite, weight loss, or leptin resistance (Medina, 2000; Haghighatdoost, 2018).
Types of food proven to help with losing weight
So if you’re taking leptin supplements to help with appetite or weight loss, you might not see the results you’re after. In the meantime, here are some steps you can take to improve leptin resistance:
- Cut down on fats and carbs. A diet that’s higher in fats and processed carbohydrates increases inflammation in the body. More inflammation can lead to leptin resistance (De Souza, 2005; Ghanim, 2009).
- Eat more protein. When you have this condition, getting rid of excess leptin may improve sensitivity to it (Zhao, 2019). Studies have found that participants who ate a high-protein diet saw decreased leptin levels and increased feelings of fullness (Weigle, 2005).
- Get enough sleep. When you’re busy, it’s tempting to skip sleep in order to get more things done. But not getting enough sleep can affect leptin levels, which impacts your metabolism and can cause weight gain (Spiegel, 2004).
- Exercise. One of the many benefits of regular exercise is that it can significantly lower excess leptin circulating in your system (Reseland, 2001).
- Reduce stress. Leptin levels are also closely tied to your emotional state (Licinio, 2015). Keeping stress in check and taking care of your mental health can help keep hormone levels balanced.
What is morbid obesity?
Leptin is an important hormone for appetite and weight regulation, but leptin supplements aren’t a helpful obesity treatment. A healthcare provider can help you determine whether you may be leptin resistant and find ways to improve your sensitivity.
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Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.