Association between the gut microbiota composition and alpha-diversity on the hormonal response and appetitive measures of individuals with obesity after a meal either rich in ultra-processed foods or without ultra-processed foods: secondary analysis of a randomized clinical trial.

Background: Obesity and the consumption of ultra-processed foods (UPF) are associated with gut microbiota composition and diversity, which may contribute to alterations in the regulation of hormones involved in satiety, given the gut microbiota's role in regulating host appetite. Therefore, this study aimed to investigate the association of gut microbiota composition and alpha-diversity at the genus-level on postprandial changes in satiety hormones, and appetitive measures in individuals with obesity, given either a meal rich in UPF or a meal without UPF.

Methods: Individuals were randomized to two groups: a) a non-UPF meal and b) a UPF meal. Both meals were matched for energy, energy density, macronutrients, fiber, and sodium content. The gut microbiota composition was analyzed using DNA metabarcoding and 16S rRNA sequencing. Alpha-diversity was assessed using the Shannon, Simpson's, and Inverse-Simpson indices at the genus level. Blood samples for hormonal (ghrelin, leptin, and GIP) and appetitive measures (hunger, satiety, fullness, and capacity to eat) were taken using visual analog scales after a 12-hour fast and 90 minutes post-meal.

Results: Twenty individuals were included in the UPF group, and 19 were in the control group, with no significant differences in gut microbiota composition or alpha-diversity indices between the groups. All hormone concentrations and appetitive measures varied significantly over time, regardless of the type of meal. A greater alpha-diversity of gut microbiota at the genus-level was associated with increased postprandial fullness (p < 0.05 for all indices), with clues that this association varied significantly between groups according to meal type (p = 0.02 for the inverse-Simpson index and p = 0.07 for the other indices), indicating a positive correlation only in the control group.

Conclusion: Gut microbiota alpha diversity at the genus level appears to be associated with the subjective sensation of fullness after a meal, and this association may vary depending on the ultra-processed food content of the meal. This finding warrants further investigation due to the exploratory nature of this study.

Trial Registration Number: RBR-56nsh92 (https://ensaiosclinicos.gov.br/rg/RBR-56nsh92).