L-glutamine and weight loss: science and myths

What is L-glutamine?

Glutamine is an amino acid, one of the building blocks of protein. When people talk about glutamine, they almost always mean L-glutamine. Glutamine exists in two forms (L and D), but it’s the L-form that the body can use, and it’s also the form found in food and in supplements.

Glutamine is considered a non-essential amino acid, meaning the body can produce it on its own, so you don’t have to get it from food. It is also the most abundant amino acid in the body, and internal production is estimated to be around 40–80 grams per day. However, in certain situations – such as after major surgery, severe trauma, burns or serious infection – needs can exceed the body’s own production. For that reason, glutamine is sometimes described as “conditionally essential”, meaning it may need to be supplied from the diet or supplements under certain circumstances.

What does glutamine do in the body?

Glutamine is especially common in tissues with high turnover, such as the gut and immune cells. It is also present in large amounts in skeletal muscle, where it acts as an important amino acid reserve. The body uses glutamine in several key processes, including:

• Immune function: immune cells use glutamine as an important fuel. It’s needed, among other things, for immune cells to multiply, produce signalling molecules (cytokines), and for certain immune cells to attack and kill bacteria.
• Gut health: glutamine is used as energy by cells in the intestinal lining and helps them renew and repair themselves, supporting normal barrier function (the gut’s “protective wall”). A strong gut barrier makes it harder for bacteria and unwanted substances to enter the body.
• Acid–base balance: glutamine can also help the body transport nitrogen, for example by carrying ammonia between different tissues. In this way, glutamine also plays a role in regulating the body’s pH.
• A building block: glutamine is part of the body’s proteins and contributes to normal protein turnover in muscles and other tissues.

Common sources of glutamine

Glutamine is found in protein-rich foods such as eggs, beef, tofu, milk, beans and lentils, and nuts, as well as foods like rice and maize. On average, we get about 6.8 grams of glutamine per day from our diet.

Glutamine is also sold as a popular supplement, often in powder form, and is mainly used in connection with training and recovery.

How much glutamine should you take per day?

Recommended daily doses of L-glutamine vary depending on the purpose, but a common dose is 5–10 grams per day.

L-glutamine and overweight/weight loss

Research on L-glutamine and weight loss is very limited and is mainly based on small, short-term studies with few participants, as well as some animal studies.

In a small pilot study from 2014 involving six women with obesity, weight and waist circumference decreased after four weeks of glutamine supplementation. However, the results are difficult to generalise because the study was so small and short.

Another study found that 30 grams of L-glutamine per day for two weeks reduced waist circumference in people who were overweight or living with obesity compared with a control group. However, there was no clear change in body weight or BMI over the short study period.

In people with type 2 diabetes, glutamine (30 g per day for 6 weeks) has also been associated with a reduced waist circumference and improved body composition, but again without weight loss.

Overall, findings are often mixed, and there is no strong scientific evidence that glutamine leads to weight loss. However, research suggests that people living with obesity often have lower glutamine levels in adipose tissue, which is linked to low-grade inflammation. This has led to theories that glutamine might reduce inflammation in adipose tissue in people who are overweight or living with obesity. In animal and cell studies, extra glutamine has been shown to reduce inflammatory signals, but it’s unclear whether the same effect occurs in humans taking glutamine supplements. After major weight loss (for example, after bariatric surgery), the lower glutamine levels in adipose tissue appear to normalise.

In summary, the evidence is weak, and more research is needed before we can say whether L-glutamine has any meaningful effect on weight, waist circumference or inflammation in humans.

So why is L-glutamine talked about in relation to weight?

A lot of claims circulate about glutamine and weight. Let’s unpack a few of them.

Claim: L-glutamine gives a flatter stomach

One theory is that glutamine may strengthen the gut lining and support renewal of gut cells, which could reduce bloating. Even though gut cells do use glutamine as fuel, there is no evidence that L-glutamine supplements on their own lead to a flatter stomach.

Bloating can have many causes, such as eating patterns, stress or constipation. How “flat” your stomach looks is also strongly influenced by genetics and body fat levels.

Claim: L-glutamine reduces sugar cravings

This claim is often based on the idea that glutamine can stabilise blood glucose and therefore reduce sugar cravings, which might make weight loss easier. The problem is that there is no solid evidence that glutamine supplements reduce cravings in a way that actually leads to weight loss. Sugar cravings are influenced by many other factors, including sleep, stress, meal regularity, and how much protein and fibre your diet contains.

Claim: Better recovery from exercise

Glutamine is sometimes promoted as a supplement that reduces muscle soreness and speeds up recovery. In theory, that could mean you’re able to train more – which could indirectly influence weight and body composition. A few studies have linked glutamine with less muscle soreness after eccentric training, but results are inconsistent and study samples are often small.

Other studies show that glutamine supplementation combined with strength training has no clear effect on performance, body composition or muscle breakdown in healthy young adults. In practical terms, L-glutamine might help in certain situations, but any effect is uncertain and likely very small.

Is L-glutamine dangerous?

For healthy adults, L-glutamine supplements appear to be well tolerated at normal doses, and intakes up to 14 grams per day are considered safe. Higher intakes (20–30 g per day) have also been tested without major side effects in short-term studies, but there isn’t enough data to draw firm conclusions about long-term use at higher doses.

People with kidney problems should avoid L-glutamine or consult a healthcare professional, as supplements are not recommended with impaired kidney function.

So what does work?

It’s easy to get stuck on individual supplements when you want to lose weight – especially when there are lots of claims about quick results. When it comes to L-glutamine for weight loss, the research is unclear and isn’t strong enough to support firm conclusions.

The good news is that other strategies have much stronger evidence behind them, and they don’t have to be complicated. Small lifestyle changes can build long-term habits that make the biggest difference for both weight and health.

Focus on a nutritious, varied diet

Build your foundation with fibre- and protein-rich foods that are nutrient-dense and satisfying. For example, eat more fruit and vegetables, root vegetables, pulses, wholegrains, fish and seafood, eggs, and low-fat dairy products. At the same time, try to reduce things that provide a lot of energy without keeping you full, such as snacks, alcohol and sugary drinks. Regular meals can also make it easier to keep a steady structure throughout the day.

Move regularly

Regular physical activity supports health, strength and function. When you’re trying to lose weight, exercise – especially strength training – is important for preserving muscle mass. Aim to increase everyday movement, add some higher-intensity activity, and combine it with strength training 2–3 times per week for best results. Training regularly also makes it easier to maintain results over time.

Prioritise sleep

Too little sleep can make it harder to reach your weight goals. One reason is that sleep loss can increase levels of the hunger hormone ghrelin. Poor sleep can also leave you more tired, making it harder to be physically active. Helpful sleep habits, such as avoiding caffeine late in the day, keeping roughly consistent sleep times, and reducing screen time before bed, can increase your chances of reaching the often recommended 7–8 hours per night.

Medicines may be an option for some people

Weight loss looks different for different people. Some reach their goals through diet and exercise, while others may need additional support. For people living with obesity, or overweight combined with weight-related diseases, modern weight-loss medicines can be an option alongside lifestyle changes.

Summary

L-glutamine is an important amino acid for the body, but there is no strong scientific evidence that it leads to long-term weight loss. Any potential effects are indirect and small. If your goal is sustainable, healthy weight loss, diet and physical activity, habits, and sometimes medical treatment, matter far more than supplements.

Would you like help understanding which tools might suit you best, or how to lay the foundations for lasting change? At Yazen, we’re here to guide you.

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