Does Melatonin Cause Weight Gain? Here's What We Know

Emily Laurence
·5 min read
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If you are one of the 70 million people in the U.S. with chronic sleep problems, there’s a good chance that you’ve looked into taking a melatonin supplement in hopes of drifting off to dreamland faster and to stay asleep longer.

Before you start taking any supplement, it’s important to know what side effects to be aware of—melatonin included. Additionally, if you are struggling with both sleep and weight loss simultaneously, it’s natural to wonder if there’s a connection between the two. Lack of sleep has been scientifically linked to obesity— so, can melatonin help or hurt when it comes to maintaining a healthy weight? Keep reading for everything you need to know.

Related: Why You Should Try a 'Coffee Nap'—and Other Surprising Tips on How to Sleep Better

What is Melatonin and When Is a Melatonin Supplement Helpful for Sleep?

“Melatonin is a hormone produced by the brain in response to darkness,” explains functional medicine doctor Dr. Wendy Warner, MD, the founder of Medicine in Balance. She explains that melatonin regulates sleep and circadian rhythm. This is why so many people who have trouble sleeping consider taking a melatonin supplement.

Dr. Sarah Wilson, ND, a naturopathic doctor and the founder and clinical director of Advanced Women’s Health, explains that there are a few instances when taking a melatonin supplement could potentially be helpful for sleep. One, she says, is if someone’s body has low levels of melatonin. The other, she says, is if someone’s body responds well to high levels of melatonin.

Related: Can You Overdose On Melatonin?

“What’s important to remember is that melatonin and cortisol [aka the ‘stress hormone’] are at opposite ends of a teeter-totter. When cortisol levels are high, melatonin levels are lower,” Dr. Wilson says. “So when we want to induce sleep, we want cortisol levels to be nice and low.” Dr. Wilson says that besides cortisol, there are other hormones involved in sleep regulation, namely norepinephrine and epinephrine. These hormones are also involved in the “fight or flight response,” and when levels are high, it is harder to relax and sleep well.

Dr. Wilson says that in these instances, taking a melatonin supplement may help someone fall asleep, but may not help them stay asleep. Truly no supplement is a replacement for getting to the root cause of stress in your life and managing these stressors. If you do want to take a melatonin supplement for sleep, Dr. Warner says it’s best to take it regularly and not intermittently, the way someone may take an occasional Ambien. The reason for this, she says, is because the hope is that the melatonin supplement will help normalize circadian rhythm, which happens over time.

Both doctors say that melatonin’s role in the body is not limited to sleep regulation. Both say that it’s linked to reducing inflammation and even cancer prevention. These are other reasons why someone may consider taking a melatonin supplement.

Related: 'I'm a Sleep Physician With Chronic Insomnia—Here's the Advice I Give to Patients'

What are Melatonin’s Side Effects and Does It Cause Weight Gain?

Before taking any supplement, it’s best to talk to your primary care doctor—especially if you have any underlying health conditions or take any medications. As with many supplements, some who take melatonin can experience side effects. If someone takes a too low dose, Dr. Warner says they likely won’t notice an effect at all. “At too high a dose, one might feel tired, have a headache, or experience brain fog the next morning,” she says, adding that a typical dose is anywhere from between one to 10 milligrams.

In terms of if melatonin can cause weight gain, both doctors say that there is no evidence of this. In fact, they say that melatonin could actually indirectly lead to healthy weight loss because of the link between poor sleep and weight gain. Scientific studies show a direct link between good sleep and healthy weight loss, so if a melatonin supplement is helping someone sleep better, it could then support weight loss as a health goal.

Dr. Wilson points out that many people who seek out a melatonin supplement likely have a disrupted circadian rhythm. This means that cortisol levels may perhaps be high. Scientific studies have shown a connection between high cortisol levels and weight gain, particularly in the form of belly fat. When this is considered, it makes sense that someone either thinking about or taking a melatonin supplement could be struggling with weight gain.

“The circadian rhythm is your body's 24-hour clock and scientific research suggests that those with an altered circadian rhythm, such as night shift workers, have a higher tendency towards weight gain due to a number of different changes in hormones because of dysfunctional circadian rhythms,” Dr. Wilson says.

She adds that it’s not just night shift workers who may experience these disruptions. “We also know that there's a phenomenon called social jetlag, where someone essentially experiences a shift in their circadian rhythm because of social activities,” Dr. Wilson explains. Whatever the reason is for the circadian rhythm being disrupted, Dr. Wilson says that this is more likely the cause of weight gain, not taking a melatonin supplement.

While a melatonin supplement may help with sleep, other habits can have an impact as well. Eating nutrient-rich foods, exercising regularly and managing stress are all linked to good sleep. And not so coincidentally, they’re all linked to healthy weight loss too. To this end, there are many factors that affect both weight and sleep. If you focus on getting good sleep, it’s likely that healthy weight loss will follow—a win all the way around.

Next up, find out how sleep experts actually want you to use melatonin. (It's not how you think!) 

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