Seeking to maintain a healthy weight is clinically relevant to billions of people worldwide. Obesity is a public health concern that can negatively impact overall health, including promoting unhealthy inflammatory responses and affecting cardiometabolic, gastrointestinal (GI), endocrine, and immune health. Over the past decade, research has explored the potential role of L-glutamine (glutamine) in supporting healthy weight management.  

Glutamine, a nonessential amino acid, plays a crucial role in protein, amino acid, and nucleotide synthesis. It contributes to overall homeostasis, regulates GI health and gut barrier function, and acts as an energy source for certain immune cells. Furthermore, glutamine supports healthy lipid and carbohydrate metabolism. During times of stress or illness, such as diabetes, the body's demand for glutamine increases, necessitating dietary or supplemental intake.

A systematic review of 47 studies and a meta-analysis of 25 trials examined the effects of glutamine supplementation on athletes. While the researchers found no significant effect on lean body mass and fat mass, they did observe an inverse correlation with body weight. Clinical studies involving soccer players (n = 20) and non-athlete male students (n = 30) demonstrated that those consuming glutamine supplements for 8 weeks experienced increased body weight and lean mass and significantly reduced fat mass. These variations may be attributed to differences in serving size, duration, and glutamine intake.

Glutamine may contribute to healthy weight management by promoting normal insulin metabolism. Evidence from a systematic review comprising 19 clinical trials and animal studies suggests that glutamine supplementation may promote healthy glucose metabolism and support healthy insulin production. This may be clinically relevant for individuals with diabetes.

In a small pilot cross-over study, six obese and overweight female patients received either glutamine supplementation or an isonitrogenous protein supplement for 4 weeks, without any changes to their diet or lifestyle. After a 2-week washout period, they switched to the other supplement for an additional 4 weeks. Only the groups receiving glutamine supplementation experienced a significant decline in body weight and composition. Insulin and HOMA-IR levels also showed a notable reduction after glutamine supplementation, although it was not statistically significant.

Promoting a healthy GI microbial environment may help to maintain a healthy body weight. In a small pilot study with 33 overweight and obese adults, participants received daily supplementation of either glutamine or a control supplement for 2 weeks. The group receiving glutamine supplementation exhibited statistically significant differences in the Firmicutes and Actinobacteria phyla compared to those in the control group. Moreover, the ratio of Firmicutes to Bacteroidetes, a good biomarker for obesity, decreased in the glutamine group from 0.85 to 0.57, whereas it increased from 0.91 to 1.12 in the control group.

Glutamine has the potential to support healthy weight management by promoting normal insulin metabolism, healthy body composition, and promoting a healthy GI microbial environment and gut barrier integrity. However, further research with more extensive clinical trials is needed before definitive conclusions can be drawn.

By Danielle Moyer, MS, CNS, LDN