Does L-glutamine promote weight loss?

Whether you’re scrolling through social media or strolling the aisles of a drugstore, you may start to feel like there’s been an influx of slim-down supplements—including those featuring L-glutamine for weight loss. 

L-glutamine is an amino acid that plays a role in many aspects of your health and can provide potential perks, such as improved gut health and a strengthened immune system. But can it also help you shed pounds? Here, we explore the possible link between L-glutamine and weight loss, take a closer look at what the research says on the matter, and share what to keep in mind before adding the amino acid to your routine.

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L-glutamine is one of 20 amino acids, which are the building blocks of protein. Nine amino acids are considered essential, meaning you must obtain them through diet because your body cannot produce them. The other 11, including L-glutamine, are nonessential. Your body can synthesize them but you can also get them through diet—e.g. meat, poultry, spinach, cabbage, and other foods—or supplements. 

The majority of L-glutamine synthesis takes place in the skeletal muscle, which acts as the primary site for production and storage of the amino acid. That said, the liver also contains a high concentration of L-glutamine, and both the liver and brain contribute to its synthesis. 

 As the most abundant amino acid in the human body, L-glutamine is involved in several bodily functions. It’s mainly associated with its roles in gut microbiota and immunity, though it may also play a part in athletic endurance. For example, L-glutamine helps preserve the intestinal barrier and provides fuel for immune cells.  

L-glutamine supplements are over-the-counter (OTC) dietary supplements that provide the amino acid in a quick, convenient form. They take on many forms, including capsules and powders, and you can typically find them wherever supplements are sold (e.g. drug stores, health food stores, Amazon). 

L-glutamine supplements are often marketed for their potential benefits for some areas of gut health and exercise recovery. There’s some research behind this: In athletes, one study demonstrated that l-glutamine supplementation reduced some markers of muscle damage. The potential perks for gut health perks are mainly due to L-glutamine’s positive effects on the gut microbiome—it can improve the balance of bacteria in the gut and reduce gut inflammation.  Studies show that when combined with a low-FODMAP diet (an eating plan that limits hard-to-digest carbohydrates), L-glutamine supplements may also improve symptoms of irritable bowel syndrome (IBS). 

In a word? Maybe. 

The research on l-glutamine and its effects on weight loss is scarce, and much of the scientific literature that is available involves animals. That said, there are some small and older studies focusing on the amino acid’s potential impact on weight, though they don’t come without their caveats (think: small in size and published a while ago). 

In a small study from 2014, six females with obesity or overweight took glutamine supplements for four weeks and experienced a significant decline in body weight and waist circumference without changing their diet or lifestyle.

A meta-analysis of 47 studies and 25 trials linked L-glutamine supplementation to a small yet significant reduction in body weight among athletes. However, the review indicated that it had little to no impact on other parts of body composition, such as fat mass and lean body mass.

Not all of the research agrees because additional findings suggest that L-glutamine may be effective at improving body composition in those with type 2 diabetes. One study involving 66 people with type 2 diabetes found that taking 30 grams of L-glutamine powder per day yielded a significant reduction in waist circumference and increase in fat-free mass. Though there were some changes in body composition, there weren’t meaningful changes in body weight and overall body mass index (BMI).

In another study, researchers observed the effects of L-glutamine on both animals and humans. The animal portion of the study found that L-glutamine reduced weight gain in rats fed a high-fat diet. In humans—all of whom had obesity or overweight—the amino acid reduced weight circumference, though it didn’t change body weight or BMI.

Remember, though, all of the above studies involved small sample sizes or animals, and it has been years since they’ve been published. More research is needed to truly determine how, if at all, L-glutamine can help with weight loss, especially because some of the data are conflicting.

Dietary supplements may come with risks and side effects, and L-glutamine is no exception. For starters, supplements are not regulated by the US Food and Drug Administration (FDA). This means that they don’t have to go through the same rigorous review for efficacy and safety that prescription medications have to undergo before going to market. 

What’s more, taking any amino acid supplement, including L-glutamine, can have adverse side effects, according to research. Some of the most common side effects of L-glutamine include:

• Constipation

• Nausea

• Headache

• Abdominal pain

• Cough

• Pain in the back, legs, feet, hands, or arms

Be sure not to use too much if you are facing certain health issues, such as cancer or liver disease, because the substance may not be ideal in those situations. For example, tumor tissue cells utilize L-glutamine faster than normal cells, which researchers suggest may be harmful for those with cancer. There have also been reported cases of liver injury in patients taking L-glutamine powders, so if you have pre-existing liver damage, it may not be a good idea to add it into your routine.

Point being: It’s important to consult a healthcare provider before adding any new supplements (L-glutamine included!) to your routine. 

First thing’s first, talk to your healthcare provider. They’re best equipped to review your medical history, current medication and supplement routine, and health goals and determine whether taking L-glutamine for weight loss might be worth a try for you. That said, here’s a little bit of a preview, if you will, of what your provider may discuss with you if they decide L-glutamine supplementation is safe and a fit for you. 

As mentioned above, L-glutamine can be obtained through diet or supplementation. Foods high in the amino acid include both plant and animal proteins, such as the aforementioned meat (e.g. beef), poultry, spinach, and cabbage as well as pork, dairy products (e.g. skim milk, ricotta cheese), parsley, tofu, corn, and eggs. 

When it comes to supplementation, you can find L-glutamine in a capsule or powdered form. In many of the human studies focused on weight loss, participants took L-glutamine powder at various doses. For example, in some studies, patients took 30 grams of L-glutamine powder (split into three equal doses of 10 grams of powder) per day. In others, patients took 0.5 grams per kilogram of body weight per day. L-glutamine powder is typically mixed in 8 ounces of liquid or 4–6 ounces of soft food like yogurt.

While there is some evidence that L-glutamine can promote weight loss, there isn’t an abundance of research on it. The good news? There are other strategies that are backed by more evidence showing they may help you lose weight.

Eat a varied diet

Though they seemingly get all of the hype, short-term fad diets aren’t the answer to sustainable weight loss. Rather, researchers recommend a slow and steady approach that involves eating a balanced diet composed of fruits, vegetables, whole grains, lean proteins, and foods with healthy fats. It also means reducing your intake of added sugars, refined carbohydrates, and processed foods—all of which have been shown to contribute to weight gain. 

Exercise regularly

Consistent physical activity can help burn calories, which is key for weight loss. It can also promote changes in body composition by reducing total fat mass. The general recommendation is to get 150 minutes of moderate aerobic activity—which, BTW, is associated with decreased abdominal visceral fat (belly fat) in those who are overweight —or 75 minutes of vigorous activity weekly. On top of that, strength training twice a week is typically advised; it can build muscle, increasing how many calories you burn at rest.

Get more sleep

Failing to get ample shut-eye can hinder your ability to meet your weight loss goals. In fact, research found that individuals who frequently got less than 7 hours of sleep per night were more likely to have a higher body mass index and develop obesity. This is due, in part, to the fact that sleep deprivation can elevate levels of ghrelin (the “hunger” hormone). It can also increase fatigue, which may be an obstacle to regular exercise. Practicing good sleep hygiene—e.g. limiting caffeine intake after a certain time, following a consistent sleep schedule, avoiding devices before bed—can boost your chances of scoring the 7–9 hours of sleep per night that the experts recommend.

Consider weight loss medications 

When it comes to weight loss, there’s no one size-fits-all experience. Some people may be able to achieve their goals just by following the more so-called traditional tactics (see: above) while others may benefit from adding a little extra boost to their routine. If the latter case sounds familiar, then it might be worth considering medications, such as Wegovy (semaglutide) and Zepbound (tirzepatide). These prescription drugs are FDA-approved for people with obesity or overweight and a weight-related health condition (e.g. type 2 diabetes) when taken alongside diet and exercise. 

Interested? Schedule an appointment with a healthcare provider in person or online, such as through Ro, which offers access to weight loss medications as well as personalized support to help you safely and effectively reach your goals. 

Though it’s considered nonessential, L-glutamine is important for many bodily functions and associated with several potential benefits, one of which may be weight loss. Keyword being “may,” as the current research on L-glutamine and weight loss is mixed and more, larger studies on humans are needed to prove the how, if at all, the amino acid can help you slim down. If you’re still interested in including L-glutamine in your weight loss journey, then be sure to consult a healthcare provider to discuss whether the amino acid—and/or other strategies—could be a fit for you.

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

October 18, 2024

Written by

Lacey Muinos

Fact checked by

Raagini Yedidi, MD

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About the medical reviewer

Raagini Yedidi, MD

Raagini Yedidi, MD, is an internal medicine resident and medical reviewer for Ro.