(P08-017-23) Patients With Anorexia Nervosa Exhibit Significant Deficits in Energy Harvest: The Role of the Gut Microbiota in Nutrient Absorption Before and After Clinical Renourishment

Objectives: The gastrointestinal tract, and the microorganisms harbored within (i.e., the gut microbiota), radically adapt to an environment restricted of nutrients; however, little is known about the impact of severe and prolonged caloric restriction in nutrient intake disorders, such as anorexia nervosa (AN), on intestinal epithelial function. The purpose of this study was to characterize the impact of prolonged nutrient deprivation on the absorptive capacity of the gut in individuals with AN.

Methods: We examined previously collected fecal samples from non-eating disorder controls (n=123) and patients with AN (n=106) before and following clinical treatment at three eating disorder units in Chapel Hill, NC, Denver, CO, and Fargo, ND. Fecal pellets were incubated at 65°C for 48 hours and used to determine the energy content of stool samples via bomb calorimetry using the Parr 6200 Calorimeter with a Parr 6510 water handling system. Calorie loss from stool was calculated as (i) calories per g of sample and (ii) relative energy content (number of calories in a stool sample divided by the number of calories consumed the previous day). Differences in stool calorie loss were identified using one- or two-way ANOVAs and unpaired and paired t-tests, when appropriate.

Results: Preliminary analysis on a subset of samples indicates that the impact of inpatient treatment on energy harvest capacity in patients with AN was consistent between treatment units (p < 0.001). The AN microbiotas had a significant deficit in the ability to harvest calories from the gut (indicated by increased relative stool calorie loss) prior to renourishment (cases: 3.28 ± 0.47 cal/g; controls: 2.11 ± 0.32 cal/g; p< 0.001). Weight, BMI, and energy harvest in patients with AN marginally improved as renourishment progressed but remained distinct from controls.

Conclusions: Patients entering treatment for AN have a dysfunctional gut that may contribute to reduced energy harvest capabilities and complicate or prolong weight restoration efforts. Future work will elucidate associations between energy harvest and specific microbial groups, as these findings have the potential to inform precision nutrition interventions encompassing microbiota-directed complementary foods.

Funding Sources: This work was funded by the NIMH and received support from the UNC Nutrition Obesity Research Center.