Leptin: What Is It, Reference Ranges & Treating High Levels

Updated in March 2023

Leptin is a hormone that helps to regulate hunger and metabolism, It stimulates energy burning and decreases the urge to overate, which can help with weight maintenance. 

When the body has many fat cells, which can happen in cases of excess weight, leptin levels tend to be higher, which temporarily decreases hunger and eating.  

Over time, contantly high leptin levels cause a resistance within the body, which decreases the brain’s response to this hormone. This leads to constant hunger, decreased energy burning and eventual weight gain. 

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Main functions

Leptin is a hormone that is released by fat cells for the following reasons: 

  • Appetite control, to decrease eating 
  • Metabolism regulation, which promotes weight maintenance 
  • Stimulation of energy burning, which promotes weight loss 
  • Regulation of blood sugar levels, to decrease glucose production in the liver 

In addition, it is thought that leptin is also involved in immune system modulation. This hormone activates defense cells that act to combat infections. 

Relationship between leptin and weight loss 

Leptin is referred to as the weight loss hormone because when it is within normal levels, it acts on the brain to decrease hunger. It also helps to regulate metabolism and burn body fat. 

Excessive production of leptin, which happens with leptin resistance, means that the brain will not react as readily to leptin. This can lead to increased hunger and more difficulty with weight loss. 

Difference between leptin and ghrelin

Ghrelin is a hormone produced by the stomach and intestines. It is responsible for stimulating a hunger sensation in the brain. Ghrelin increases mainly during fasting, and can be high in cases of anorexia and cachexia. 

Leptin is a hormone that is produced by the fat cells. It acts on the brain to control appetite and metabolism and promotes energy burning. Leptin can become high in people with excess fat cells, like in people with obesity. 

Reference Ranges

Normal leptin levels vary depending on sex, BMI and age: 

  • Children between 5 and 9 years: 0.6 to 16.8 ng/mL
  • Children and teens between 10 and 13 years: 1.4 to 16.5 ng/mL
  • Teens between 14 and 17 years: 0.6 to 24.9 ng/mL
  • Women with a BMI between 18 and 25: 4.7 to 23.7 ng/mL
  • Women with a BMI over 30: 8.0 to 38.9 ng/mL
  • Men with a BMI between 18 and 25: 0.3 to 13.4 ng/mL
  • Men with a BMI over 30: 1.8 to 19.9 ng/mL

Leptin results may vary depending on the person’s health status. They can also appear higher due to inflammatory substances or other hormones, like insulin or cortisol.

Other factors can decrease leptin levels, like weight loss, smoking or prolonged fasting. 

How to evaluate leptin levels

Leptin levels can be assessed with bloodwork ordered by a doctor. 

To test leptin levels, you should fast for 12 hours, although some labs will only require 4 hours of fasting. Be sure to check the prep instructions with your doctor or lab before this test. 

High leptin levels

High leptin levels, also known as hyperleptinemia, generally occurs in cases of obesity, as increased fat cells stimulate the production of this hormone.

High levels eventually cause the brain to stop relying on leptin stimulation for appetite management. This is also known as leptin resistance, which increases your hunger and overall fat-burning mechanisms. It can make weight loss more difficult and lead to weight gain. 

How to treat high leptin

Some ways to regulates leptin levels and prevent leptin resistance include:

1. Gradual weight loss

Sudden weight loss can lead to decreased leptin levels. The brain perceives this to be a phase of food restriction, and sends out signals to promote appetite and eating. This can make maintaining a weight more difficult. 

With gradual weight loss, leptin levels will also reduce slowly, which will help with appetite control and weight goals. 

2. Avoiding inflammatory foods

Some inflammatory foods, like those that are rich in sugar (e.g. candy, soda, cake, ice cream) and fat (french fries, fat food, sausage) cause inflammation on a cellular level, which can promote leptin resistance. 

3. Maintaining a varied, healthy diet 

Maintaining a balanced diet and consuming the appropriate amount of calories can aid healthy weight loss and prevent excess body fat accumulation, which reduces overall risk for leptin resistance. 

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4. Performing exercise

Exercising regularly helps with weight loss or maintainance, which allows leptin levels to stay within normal levels to regulate metabolism. Some activities that can help to balance leptin levels include running, long walks, strength training and HIIT. 

Before starting any exercise plan, you should see a doctor and speak with a personal trainer to prevent injuries. 

5. Plenty of sleep

Poor sleep can decrease leptin levels in the body, leading to increased appetite. Sleeping less than 7 hours per night can also increase cortisol levels, which slows metabolism and makes weight loss more difficult. 

6. Medication

Some medications are being studied to treat insulin resistance. However, there are no studies that prove their total efficacy against this condition.