Gut Microbiome and Anorexia Nervosa in Adolescents

Introduction 

Gut microbiome and anorexia nervosa increasingly show a strong connection, as emerging research highlights the role of gut bacteria in the development and treatment of this complex psychiatric disorder. Anorexia Nervosa (AN) is a prevalent psychiatric syndrome, with 95% of cases being women.

The Study

56 patients diagnosed with AN or atypical AN between 12 to 20 years of age were longitudinally studied to determine the clinical factors that lead to development or remission of intestinal dysbiosis in AN. The effects of body mass index, calorie intake, hormone restitution and illness duration on intestinal microbiome were studied, in addition to whether the gut microbiome could help predict weight gain and relapse.

Anorexia Nervosa

It can be classified into the common restricting (AN-RS) type and the less common binge-eating or purging (AN-BP) type.¹ In adolescent girls, it is the third most prevalent chronic disease.²

Researchers have not yet fully understood the pathophysiology, but it involves restricted energy intake, significant weight loss, distorted body image, and increased physical activity. Specialists can manage AN through multidisciplinary approaches, but fewer than half of patients achieve complete remission.

Mortality Rate

It holds the highest mortality rate among psychiatric conditions, with a standardized mortality ratio 5-10 times higher than that of healthy control.²

What is Intestinal dysbiosis

Intestinal dysbiosis is an imbalance between beneficial and harmful gastrointestinal microorganisms. It has been implicated in many psychiatric conditions, including AN. Gut microbiome may play an important role in the pathophysiology of AN by affecting energy metabolism, weight regulation, and the brain-gut axis.

Understanding how gut microbiome and anorexia nervosa interact could open new pathways for improving recovery outcomes in young patients.

Anorexia nervosa and intestinal dysbiosis

Disruption in the communication between the gut microbiome, the intestinal system, and the brain may contribute to the risk and progression of AN. Individuals with AN often exhibit an imbalanced gut microbial community (dysbiosis), which may even emerge prior to the clinical onset of the disorder. 

The gut microbiome plays a key role in regulating the host’s immune system, metabolism, and brain activity through various pathways. Through the gut–microbiome–brain axis, it can influence brain functions such as appetite control, mood, and behavior.

Dysbiosis may impair nutrient absorption (like amino acids and vitamins), alter energy extraction, affect the production of bioactive compounds, disrupt neurotransmitter breakdown, and increase intestinal permeability. These disruptions may help explain the connection between dysbiosis and AN. 

Who took part in the study

The study involved 57 adolescent inpatients diagnosed with anorexia nervosa, aged between 12 and 20 years, and 34 age-matched healthy controls. Patients were monitored at up to nine time points, including a 1-year follow-up, while controls were assessed at up to six time points.

Study design and procedures 

Researchers conducted a longitudinal analysis using 16S rRNA gene sequencing to profile the gut microbiome from fecal samples collected at multiple intervals: upon hospital admission, during inpatient treatment, at discharge, and at a 1-year follow-up.

Researchers recorded clinical data, including dietary intake, weight changes, and hormonal levels (e.g., leptin). They performed statistical analyses to identify associations between microbiome composition and clinical outcomes, such as weight recovery and hospital readmission

This study involved longitudinal tracking of changes in gut microbiome composition among adolescents with AN, both during inpatient treatment at low body weight and one year post-discharge while on a home-based diet. Clinical variables such as illness duration, degree of weight loss, and body weight at admission were assessed to determine their impact on the microbiome.

Additionally, the study examined how nutritional intake, weight gain, and hormonal recovery influenced microbial shifts throughout treatment. Finally, researchers investigated whether baseline microbiome characteristics could serve as predictive markers for future weight progression and risk of relapse.

Key findings 

Microbiome Alterations

Researchers observed significant differences in gut microbiome composition between AN patients and healthy controls, especially during the acute starvation phase. These differences diminished as patients gained weight and became least pronounced at the 1-year follow-up.

Clinical Associations

At the time of hospital admission, the structure of the gut microbiome showed a strong association with how long the illness had lasted and the extent of previous weight loss.

During treatment, changes in the microbiome were associated with caloric intake, weight gain, and hormonal recovery (e.g., leptin levels).

Significant clinical factors that influence the microbiome in patients with AN include illness duration and the amount of weight loss.

The microbiome underwent changes throughout the treatment period but continued to differ, at least in part, from that of healthy controls at every time point—including in patients considered weight-recovered at the 1-year follow-up.

The primary factors driving these microbiome differences are the disease and its effects, rather than differences between hospital and home-based diets.

Predictive Biomarkers

The abundance of certain bacterial genera at admission such as Sutterella, was predictive of better clinical outcomes, including higher body weight at the 1-year follow-up. In contrast, certain microbial taxa were linked to a higher likelihood of being readmitted to the hospital.

What does the study highlight 

For patients with AN, the gut microbiome plays a major role in the pathophysiology of the disease. 

Factors such as kilocalories intake, weight gain and hormonal recovery affect gut microbiome. 

The microbiome profile at the time of admission holds predictive value for the progression and outcome of the disease. This can assist in categorizing patients at the time of admission and tailoring treatment intensity to those who need it most.

Sutterella may offer potential for developing microbiome-based therapies that could complement current treatments for anorexia nervosa in the future.

Treatment and weight gain reduce dysbiosis in AN patients.

Conclusion

This study highlights the dynamic nature of the gut microbiome in adolescents with anorexia nervosa and its association with clinical outcomes. The findings suggest that specific microbial profiles could serve as prognostic indicators and potential targets for therapeutic interventions aimed at improving treatment efficacy and reducing relapse rates in AN patients.

References 

1. Fan Y, Støving RK, Berreira Ibraim S, Hyötyläinen T, Thirion F, Arora T, et al. The gut microbiota contributes to the pathogenesis of anorexia nervosa in humans and mice [Internet]. Nature Publishing Group; 2023 [cited 2025 Jun 16]. Available from: https://www.nature.com/articles/s41564-023-01355-5 
2. Anton-Păduraru D-T, Trofin F, Nastase EV, Miftode RS, Miftode I-L, Trandafirescu MF, et al. The role of the gut microbiota in anorexia nervosa in children and adults-systematic review [Internet]. Multidisciplinary Digital Publishing Institute; 2023 [cited 2025 Jun 16]. Available from: https://www.mdpi.com/1422-0067/25/1/41 

Written By : Bede Chukwudi Ugwuoke

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