Leptin Resistance 

People living with obesity usually have high leptin, not low leptin. But the brain stops responding to it — a problem called leptin resistance.

When the brain stops hearing leptin’s signal, it acts as though the body is starving, even when there is plenty of stored fat. When you lose weight, leptin levels decrease and can signal the brain that it is starving–especially if you lose the weight too quickly. When leptin levels drop, the following happens:

  • Increase hunger

  • Slow metabolism

  • Reduce thyroid hormone activity

  • Increase inflammation

  • Make weight loss very difficult

This is one reason “eat less, move more” often fails long-term — leptin pushes the body to regain weight after dieting.

Why Leptin Resistance Happens

Modern research shows several causes:

1. Chronic inflammation

Inflammation blocks leptin’s signal in the brain. This is why inflammatory lifestyles — high sugar, poor sleep, stress — make weight loss harder.

2. High insulin levels

Insulin and leptin talk to each other. When insulin is high (from sugar, snacking, refined carbs), leptin signaling becomes weaker.

3. Sleep deprivation

Even one poor night of sleep increases hunger hormones and lowers leptin sensitivity.

4. Ultra-processed foods

Studies show processed foods cause higher calorie intake and disrupt satiety hormones — including leptin.

How to Support Healthy Leptin Function

  • Eat whole foods with lots of vegetables and protein

  • Avoid grazing/snacking between meals

  • Get 7–9 hours of sleep to restore hormone balance

  • Manage stress, which affects cortisol and leptin together

  • Avoid refined sugar and flour, which increase both insulin and inflammation

  • Exercise regularly, especially walking and strength training

Even small changes can help leptin signal more clearly again.

Bottom Line

Leptin is not just a “fullness hormone.” It affects metabolism, thyroid function, immunity, fertility, inflammation, and long-term weight control. When leptin stops working correctly — leptin resistance — the body fights to hold on to weight.

Understanding leptin helps explain why dieting alone rarely works and why whole-body approaches to health are so important.

For a deeper dive, see: “Why Diets Make You Fat” and “Hormones and Weight Loss”