Melatonin and its surprising effects on fat loss

Created on: February 17, 2021

Did you know? While you’re asleep every night, you lose a little bit of weight. It’s true, your body naturally sheds weight through sweating and exhalation. Although sleep is an idle activity, the body stays busy burning approximately 50 calories per hour. Your weight will naturally continue to fluctuate throughout the day, but good quality sleep may just help keep unwanted fat off.

How does melatonin affect fat loss?

Melatonin, the sleep hormone, influences fat loss with the help of a variety of hormones and processes responsible for stress, blood sugar and appetite. Weight loss has often been simplified to calories in vs. calories out, but it’s much more complex than that. While a melatonin supplement is certainly not a magic pill for shedding weight, it does have a role to play in weight management specifically when it comes to fat loss.

What are fat cells and what purpose do they serve?

Over the years, fat has gotten a pretty bad reputation, but fat cells have a few important jobs. They collect in the adipose tissue, where they are sometimes referred to as adipocytes. There are three types of fat cells: white, beige and brown. While all three serve an important purpose, brown and beige are often referred to as “good fat”. The primary functions of fat cells within the adipose tissue include hormone secretion, thermogenesis and energy storage and production. Adipose tissue is also used for insulation and organ protection. However, too much can be harmful and lead to a number of issues including cardiovascular disease, diabetes and hormonal imbalance.

Which processes does adipose tissue affect?

Endocrine Function

Adipose tissue is classified as an endocrine organ, which means it secretes hormones. Fat cells communicate with other endocrine organs, glands and body systems by releasing hormones involved in appetite, blood sugar, immune function, inflammation, blood pressure and ovulation.


Thermogenesis is the process by which brown and beige adipose tissue break down and “burn” fatty acids to be used by the mitochondria to generate heat. Compounds that increase thermogenesis are commonly found in weight loss supplements to increase metabolism and burn fat.

Energy production and storage

In adipose tissue, mitochondria are responsible for producing ATP – the energy and fuel for all cellular processing. Each brown and beige fat cell is densely packed with mitochondria, resulting in a great ability to produce energy. Conversely, white fat cells have very few mitochondria, making them inefficient energy producers. Their primary function is to store energy for later use.

The art of influencing fat cells

Unless you have a dramatic change in weight, you will maintain the same number of fat cells from puberty into adulthood. Despite this, there are ways to influence the size and type of fat cells. We ideally want to increase “good” brown and beige adipose tissue, while decreasing “bad” white adipose tissue. Adipose tissue is affected by diet, exercise, body temperature and thyroid function. It’s also affected by – you guessed it – melatonin!

The effects of melatonin on adipose tissue

One of melatonin’s most important tasks is ensuring that metabolic functions line up with the circadian rhythm. When these systems are out of sync, we tend to see a rise in obesity and metabolic syndrome. Melatonin helps to boost brown adipose tissue, while melatonin deficiency actually decreases the efficiency of thermogenesis. Rather than storing fat, melatonin assists in turning fat into energy, and helps to protect mitochondrial integrity through its potent antioxidant capacity.

A coalition of hormones

Melatonin affects and is affected by other hormones and systems involved in fat loss including:
  • The stress hormone (cortisol)
  • Blood sugar (insulin and adiponectin)
  • Appetite regulation (leptin and ghrelin)

Stress: The culprit behind weight gain

Stress has numerous effects on nearly all bodily functions including melatonin production, blood sugar control and fat storage. Melatonin and cortisol are intended to be in opposition. In the morning, as melatonin production decreases, cortisol increases to help get you out of bed, and the opposite is true in the evening. During times of stress, high cortisol levels can result in decreased melatonin production. This leads to overeating, blood sugar imbalance, fat storage and as a result, a tough time getting to sleep. Stress induced fat storage is more likely to accumulate around the abdomen, which can increase the risk of other health complications such as cardiovascular disease, cancer and diabetes.

Melatonin and blood sugar

Blood sugar is controlled by a variety of factors including melatonin and adiponectin – two hormones that work together to ensure proper insulin sensitivity and production. Adiponectin is a hormone secreted by fat cells that increases insulin sensitivity, and helps to reduce inflammation. A study of postmenopausal women shows that melatonin supplementation produces a significant increase in adiponectin. In this study, the women supplementing with melatonin decreased fat mass by 7%, and increased adiponectin by 21% compared to the placebo group over one year. Inversely, inadequate melatonin and adiponectin results in the potential for insulin resistance, which can lead to type 2 diabetes. An increase in circulating insulin encourages fat storage and prevents proper use of fat as energy.

The key to your appetite

Appetite is controlled by a number of hormones including ghrelin, a hormone that stimulates appetite and promotes fat storage, and leptin, the appetite supporessor. When the body is sleep deprived or deficient in melatonin, more ghrelin and less leptin is produced. This results in increased food intake and fat storage. Ghrelin is decreased when melatonin levels are adequate. Synthesis, release and proper functioning of leptin is directly influenced by melatonin and insulin.

Melatonin for fat and weight loss

Using melatonin for sleep is just the tip of the iceberg. Aside from the positive effects listed above, research shows potential benefits for IBS, endometriosis, hormonal health, immune function and inflammation. Though melatonin isn’t a magic solution for shedding fat quickly, adequate levels and a good night’s sleep certainly doesn’t hurt!