‘Why Can’t I Get Full?’ Experts Reveal a Widespread, but Rarely Discussed, Problem with America’s Appetites

Updated: Sep. 08, 2023

Leptin resistance "often flies under the radar, making it challenging for individuals to identify the underlying cause of their weight struggles," one doctor told us.

No matter where you stand on drugs like Ozempic and Wegovy—which were developed to help diabetes patients but are being used more widely as weight-loss medications—one positive contribution they’ve made has been to create awareness that being overweight is often not because of a lack of willpower. Many people truly just experience hunger to varying severities based on individual biology and physiology.

If you’re known to eat what feel like large amounts of food before you feel full (as one individual on our editorial team sympathized: “I don’t feel full unless I’m Thanksgiving full!”), it could be due to this clinical issue. And while many of us have heard about insulin resistance, which can lead to diabetes, there’s been much less conversation about a huge factor that’s at work behind our big appetites: Leptin resistance.

Leptin is sometimes referred to as “the satiety hormone,” which means it flags your brain when your belly is full. When leptin isn’t functioning appropriately, that’s called leptin resistance: You may feel hungry, and you may eat, when your appetite has already been assuaged.

Leptin resistance is a condition that many people are not aware of, despite its significant impact on weight management and overall health, says Stewart Parnacott, DNP, BSN, a Georgia-based doctor of nursing practice, nurse anesthetist, and instructor at Baylor College of Medicine. Dr. Parnacott tells The Healthy @Reader’s Digest: “Unlike other well-known weight-related issues, such as insulin resistance in diabetes, leptin resistance often flies under the radar, making it challenging for individuals to identify the underlying cause of their weight struggles.”

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What causes leptin resistance

When you eat, your body produces leptin, which sends signals to your brain that you are sufficiently full. Madelyn Larouche, RD, a registered dietitian from North Carolina, says leptin resistance “means [a person has] high levels of circulating leptin in their bodies, and the leptin is struggling to cross the blood-brain barrier to do its job,” Larouche says. “So, folks experiencing this may find it hard to become full at meals and feel like they can’t stop eating.”

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Dr. Parnacott notes leptin resistance isn’t tied to a willpower or self-control issue. However, research shows leptin levels can be related to how much fat is on your body, and leptin can contribute to obesity. “In reality, leptin resistance is a complex metabolic issue influenced by genetics, lifestyle factors, and hormonal imbalances,” Dr. Parnacott says. “Blaming individuals for their condition can lead to further frustration and hinder appropriate management strategies.”

Sound familiar? Here’s an added aggravation: Doctors don’t regularly diagnose leptin resistance, Larouche says. You might have to ask your doctor about it. A doctor who hears you may order a blood test to gauge your leptin levels.

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How to improve leptin resistance

Don’t expect a magic pill to fix leptin resistance: Dr. Parnacott says there aren’t specific FDA-approved medications to exclusively target it.

There are, however, a slew of supplements that promise to help leptin resistance. The problem is that they don’t come with a lot of peer-reviewed evidence to support that they actually work.

You can’t eat foods with leptin to boost your function—it’s not found in food. It can be reversed, though Larouche says lifestyle factors should be the main intervention. “Reversal of leptin resistance largely depends on the underlying factors contributing to the condition,” Parnacott says. “In some cases, addressing lifestyle habits and achieving weight loss can lead to improved leptin sensitivity. However, in other instances where genetic factors play a significant role, complete reversal may be more challenging.”

“Certain non-traditional methods, such as intermittent fasting, have shown promising effects in some individuals with leptin resistance,” Dr. Parnacott points out.

Adds Larouche: If you experience leptin resistance, “You aren’t doomed.” Eating a balanced diet, staying active physically, and getting adequate sleep can help. Evidence also shows that shifting to a low-fat diet may also help.

Knowing your leptin levels may be a good thing, because they can impact other processes in your body—including insulin activity and your metabolism.

Research, such as one 2020 study that examined the interplay between insulin resistance and leptin resistance, has shown that insulin and leptin play an important role in how prediabetes and non-alcoholic fatty liver disease develop. High levels of leptin can increase insulin resistance—a precursor to prediabetes…and diabetes.

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