Impact of Dietary Fiber as Prebiotics on Intestinal Microbiota in Obese Thai Children

The relative abundance of Bifidobacterium was determined using 16S rRNA gene sequencing from stool samples. The abundance values were then transformed into z-scores based on the distribution of the entire study population at baseline. A z-score of 0 represents the mean abundance of the population, while positive or negative values indicate the number of standard deviations above or below the mean, respectively.

Evaluation of body composition changes focusing on Fat Mass Index (FMI) and Fat-Free Mass Index (FFMI). FMI and FFMI were calculated as the weight of fat mass or fat-free mass in kilograms divided by the square of height in meters (kg/m^2). Values reported represent the change from baseline to 6 months. A positive change value indicates an increase in the respective mass index from baseline, while a negative value indicates a decrease. FFMI measures the amount of fat-free mass (including muscle) relative to height.

Change from baseline in Emotional Undereating (EUE) scores at 6 months. EUE is a subscale of the Children's Eating Behavior Questionnaire (CEBQ), consisting of items scored on a 5-point Likert scale (1 = Never, 5 = Always). The score for this subscale is calculated as the mean of its constituent items.

Mean change in serum Interleukin-15 (IL-15) concentration from baseline to 6 months. IL-15 was quantified using ELISA as part of an exploratory mechanistic analysis to investigate the gut-muscle axis. For this specific exploratory assessment, data were analyzed for the inulin group to evaluate within-group changes.

This mechanistic exploratory analysis primarily focused on the inulin intervention group. A small subset of participants from the placebo and dietary fiber groups (n=5 per group) was included for internal comparison. Summary statistics are reported for the inulin group.

Variable Importance in Projection (VIP) scores were derived from Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) to assess the contribution of each metabolite to group separation. VIP scores are continuous, non-negative values with a theoretical minimum of 0. There is no theoretical maximum or fixed upper limit for a VIP score. A value greater than 1.0 is a universally accepted threshold indicating that a metabolite contributes significantly to the model's projection. For this analysis, VIP scores are reported as single, group-level cumulative metrics derived directly from the overall multivariate OPLS-DA model. Because these are model-derived descriptive values reflecting whole-group patterns rather than participant-level summary statistics, individual-level variance does not exist, and standard deviations are not applicable.

Change in BMI Z-score from baseline to 6 months. BMI Z-score (standard deviation score) was calculated based on age and sex using the WHO child growth standards.

Changes in serum concentrations of Interleukin-1 beta (IL-1β), Tumor Necrosis Factor-alpha (TNF-α), and Interleukin-6 (IL-6) from baseline to 6 months, measured using ELISA. These markers were assessed to evaluate the effect of the intervention on systemic inflammation.

Serum concentrations of Peptide YY (PYY) measured at baseline and at the end of the 6-month intervention using ELISA. The data are reported as the mean and standard deviation for each time point to evaluate the response of this appetite-regulating hormone to the intervention.

Serum concentrations of Glucagon-like peptide-1 (GLP-1) measured at baseline and at the end of the 6-month intervention using ELISA. The data are reported as the mean and standard deviation for each time point to assess changes in this satiety-related hormone.

Distribution of gut microbiota enterotypes (e.g., Bacteroides vs. Prevotella) among participants at 6 months, determined by clustering analysis of 16S rRNA sequencing data.