The purpose of this research study is to analyze the microorganisms residing in the gut of patients with anorexia nervosa. Research has begun to link changes in the intestinal microbiota with diseases such as inflammatory bowel disease (IBS), asthma, and obesity, but although some studies have investigated the intestinal microbiota in overweight/obese individuals, very little is known about the intestinal microbiota in underweight individuals. The investigators aim to identify the enteric bacterial groups associated with adiposity, BMI, anxiety, and stress in patients with anorexia nervosa.

Anorexia nervosa (AN), a psychiatric disorder characterized by extreme weight dysregulation commonly presents with comorbid anxiety. Therapeutic renourishment in AN is based primarily on clinical opinion and guidelines, with a weak evidence base. Compelling data implicate the intestinal microbiota in the regulation of adiposity and behavior, providing a strong rationale for exploring the role of this complex microbial community in the emergence and maintenance of, and recovery from AN. The overarching goal is to understand the precise mechanism(s) by which intestinal bacteria contribute to dysregulation of adiposity, BMI, anxiety, and stress in patients with AN. The investigators hypothesize that intestinal microbiotas that arise from prolonged starvation contribute to increases in adiposity upon refeeding and to persistently elevated anxiety and stress in individuals with AN. To test the hypothesis the investigators propose 3 specific aims. In aim 1, the investigators will identify the enteric bacterial groups associated with adiposity, BMI, anxiety, and stress in AN patients. The investigators will characterize the intestinal microbiota in acutely low weight AN patients (T1), in the same patients following weight restoration (T2), and in healthy controls (HC) via high throughput sequencing of the 16S rRNA gene.

The investigators will compare the abundances of specific enteric taxa with adiposity, BMI and behavior (anxiety and stress) in this study population. In aim 2, The investigators will characterize the functional impact of the intestinal microbiota of AN patients on adiposity and BMI when transplanted into germ free (GF) mice. The investigators will transplant uncultured microbiotas from AN patients (at T1 and T2) and HC into GF mice and assess the impact of enteric microbes on adiposity. In aim 3, the investigators will characterize the functional impact of the intestinal microbiota of AN patients on anxiety and stress, and molecular biomarkers of these behaviors, when transplanted into GF mice. The investigators will transplant uncultured microbiotas from T1 AN patients and HC into GF mice and assess the impact of enteric microbes on anxiety and stress. GF mice gavaged with sterile phosphate buffer saline will be used as controls in aims 2 and 3. The proposed science is significant in pioneering the combination of large scale 16S rRNA gene sequencing-based studies of intestinal microbiotas in AN with exploration of their functional influence on adiposity and behavioral traits associated with AN. The results will provide direction on how best to test adjunct interventions for AN with pre-, pro-, anti-, or syn-biotics to enhance current approaches to therapeutic weight restoration and improve treatment outcome. The science is highly innovative as it will investigate an entirely novel factor in AN, the intestinal microbiota, and use a novel approach to identify enteric microbes that impact adiposity and behavior in this devastating illness. Additionally, the investigators will hope to study an entirely novel factor (namely, the intestinal microbiota) as a contributor to the underlying pathophysiology of AN.

Inclusion Criteria:

• Anorexia nervosa patient receiving treatment

Exclusion Criteria:

• history of gastrointestinal tract surgery
• history of inflammatory bowel diseases (IBD)
• history of irritable bowel syndrome (IBS)
• history of celiac disease
• history of any other diagnosis that could explain chronic or recurring bowel symptoms
• treatment in the last two months with antibiotics, non-steroid anti-inflammatory agents, or steroids.
• eating disorders or other major psychiatric or medical issue (for healthy controls).

Inpatient population at Eating Disorders Unit (EDU) at UNC hospitals. Healthy controls pooled through UNC listserv.