Does L-glutamine promote weight loss?

Does L-glutamine promote weight loss? The short answer: maybe, but the evidence is limited. L-glutamine is an amino acid that supports gut and immune function, and some small, early studies suggest it may modestly reduce weight and waist circumference.

But there's no strong clinical research showing that L-glutamine supplementation leads to significant fat loss on its own. It works best as part of a broader eating plan and lifestyle, not as a standalone weight loss solution.

Maybe. But probably not by itself. 

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 eating habits or lifestyle.

A meta-analysis including 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 research agrees, as additional findings suggest that L-glutamine may be effective at improving body composition in those with type 2 diabetes, potentially by supporting blood sugar regulation.

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 waist circumference, though it didn't change body weight or BMI.

Keep in mind that all of the above studies involved small sample sizes, 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.

See if you qualify

L-glutamine supplements are over-the-counter 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 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 gut health perks are mainly due to L-glutamine's positive effects on the gut microbiome — some studies suggest it can improve the balance of bacteria in the gut and reduce gut inflammation. Research suggests that when combined with a low-FODMAP diet (an eating plan that limits hard-to-digest carbohydrates), L-glutamine supplements may help improve symptoms of irritable bowel syndrome (IBS).

First things 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 trying L-glutamine for weight loss might be right for you.

That said, here's a little preview of what your healthcare provider may discuss with you if they decide L-glutamine supplementation is safe and a fit for you.

L-glutamine can be obtained through food or supplementation. Foods high in the amino acid include both plant and animal proteins, such as meat (e.g. beef, poultry, pork), fish, eggs, dairy products (e.g. skim milk, ricotta cheese), nuts,and beans and legumes. 

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) per day. In others, patients took 0.5 grams per kilogram of body weight per day. Confirm the dosage you are going to try with your healthcare provider before starting L-glutamine.  L-glutamine powder is typically mixed in 8 ounces of liquid or 4–6 ounces of soft food like yogurt.

Dietary supplements may come with risks and side effects, and L-glutamine is no exception. For starters, supplements are not as regulated by the US Food and Drug Administration (FDA) as prescription medications. 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 pose a risk for those with cancer. Although rare, 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. Supplements in general can be a risk factor for liver damage, so always be sure to get your supplements from a reputable source. 

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

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 backed by more evidence that 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 sustainable 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 is associated with decreased abdominal visceral fat (belly fat) in people with 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). 

Sleeping too little can also increase fatigue, which may be an obstacle to regular exercise. Practicing good sleep hygiene — 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 medications are FDA-approved for people with obesity or overweight and a weight-related health condition (high blood pressure) when taken alongside a healthy eating plan and exercise.

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

See if you qualify

L-glutamine is an amino acid that plays a role in gut and immune health, and some small studies suggest it may modestly support weight loss and a smaller waist circumference. But that evidence is still preliminary — the research is mixed, often involves small samples or animal studies, and doesn't establish L-glutamine as a reliable weight loss strategy on its own.

If you're still interested in including L-glutamine in your weight loss journey, be sure to consult a healthcare provider to discuss whether the amino acid — and/or other strategies — could be a fit for you.