Effects of Supplementation With Different Specificities of Dietary Fiber on Health-Related Indicators in Adults With Overweight or Obesity: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Context Dietary fiber (DF) exhibits variations in its chemical and physical complexity, as well as in its utilization by the gut microbiota. However, the impact of these differences on the health status of adults with overweight or obesity remains unclear.Objective This meta-analysis aimed to explore the varying effects of supplementing with different specificities of DF on the health of adults with overweight or obesity, providing guidance on selecting DF supplementation to improve health status.Data Sources The literature search encompassed 4 electronic databases-PubMed, Cochrane Library, Web of Science, and EMBASE-and was conducted between January 1, 2012, and November 10, 2023. Randomized controlled trials comparing DF with placebo treatment, without energy restriction, were included.Data Extraction Two independent reviewers extracted data using a standardized form, resolving discrepancies through discussion. The data included study characteristics, participant demographics, DF specifications, and outcome measures.Data Analysis Random-effects models and the generic inverse variance method were used to analyze data, assuming varying outcomes based on DF specificity. Meta-regression assessed the impact of population, duration, and dosage. Publication bias was evaluated using funnel plots and Egger's and Begg's tests. The analysis included 34 trials (n = 1804) examining DF supplementation at 1.5 to 40 g/day for 3 to 16 weeks. DF supplementation significantly reduced glycated hemoglobin (HbA1c) by 0.13%, fasting insulin by 0.82 mu IU/mL, and homeostatic model assessment of insulin resistance (HOMA-IR) by 0.33 in adults with overweight or obesity. Subgroup analyses based on DF specificity revealed differences in effects on HbA1c, fasting insulin, and systolic blood pressure. The low-specificity subgroup showed significant heterogeneity in body weight, body mass index, HbA1c, fasting insulin, and HOMA-IR, with a decrease in fasting insulin by 1.09 mu IU/mL. The low-to-intermediate-specificity subgroup had reductions in HbA1c by 0.8%, fasting insulin by 2.08 mu IU/mL, and HOMA-IR by 0.61. The intermediate-specificity subgroup experienced a 2.85-kg decrease in body weight and a 9.03-mg/dL increase in LDL cholesterol. The mixed subgroup showed an increase in systolic blood pressure by 3.85 mmHg.Conclusion Supplementing with different specificities of DF may have distinct effects on health-related indicators in adults with overweight or obesity. Considering individuals' gut microbiota composition and specific health goals is recommended when selecting DF supplementation for adults with overweight or obesity.Systematic Review Registration PROSPERO registration no. CRD42023432920.