Effect of a Mediterranean Diet Intervention with and Without Weight Loss on the Gut Microbiota in Obese, Older Adults

Abstract Objectives Evidence suggests that the gut microbiome has profound implications on human health and is modifiable by diet and weight loss. The objective of this study was to determine the impact of an 8-month Mediterranean diet (Med Diet) intervention with and without weight loss, compared to a control group, on the diversity and abundance of gut bacteria in obese, older adults. We hypothesized that adoption of an energy-restricted Med Diet to promote weight loss would impact gut microbial structure and composition the most. Methods Subjects are a subset from a larger trial that were randomized (2:2:1, respectively) to one of the following 8-month interventions: (1) Med Diet group lifestyle intervention (n = 10); (2) Med Diet plus energy restriction group lifestyle intervention (n = 10); or (3) Control (n = 5). Anthropometrics, body composition, circulating metabolic and immune markers, body composition, lifestyle behaviors, and stool were collected at pre- and post-intervention. Sequencing of the microbial 16S rRNA V4 region was performed. SAS, DADA2 and R were used to examine Med Diet adherence, weight loss, and fecal microbiota structural and compositional changes post-intervention. Results Mean BMI at baseline was 35.8 kg/m2 (SD = 4.0) and mean age was 64.8 years (SD = 6.3). The subjects were primarily female (88%) and self-described as African American (96%). At post-intervention, the mean increase in Med Diet adherence for groups (1), (2), and (3) was 3.1, 3.8, and -0.8 points, respectively, and mean % weight loss was -2.8%, -7.2%, and 0.7%, respectively. Metagenomic analysis revealed that species richness, diversity and the relative abundance of the genera Lachnoclostridium, Veillonella, and Bifidobacterium and Blautia caecimuris increased significantly post-intervention among only the energy restricted Med Diet group. Conclusions Our study shows that an energy-restricted Med Diet that promotes weight loss in older, obese adults increases gut microbial species richness and diversity, which may have positive implications for human health. Funding Sources RO1 from National Institutes of Health- National Heart, Lung, and Blood Institute.