Glucomannan and resistant starch in obesity management: a systematic review of satiety, gut fermentation, and weight-related and metabolic outcomes.

Obesity is a growing global health challenge associated with dysregulated appetite, impaired gut function, and metabolic disorders. Glucomannan and resistant starch are functional dietary fibers that may influence obesity-related pathways through distinct but interconnected mechanisms. This systematic review aimed to synthesize current evidence regarding their effects on satiety and appetite regulation, gut fermentation and microbiota-related pathways, and weight-related and metabolic outcomes. A systematic search of Scopus, PubMed/MEDLINE, ScienceDirect, and the Cochrane Library was conducted without publication-date restrictions, with the final search performed on 25 August 2026. Eligible randomized and crossover trials, non-randomized intervention studies, and animal studies investigating glucomannan, resistant starch, or relevant formulations were included when they reported predefined obesity-related outcomes. Twenty studies met the inclusion criteria, comprising six randomized or crossover trials, three non-randomized intervention studies, and eleven animal studies. Several studies reported improvements in satiety, hunger, food or energy intake, body weight, adiposity, or metabolic outcomes, although findings were heterogeneous across interventions, populations, and study designs. Glucomannan-containing interventions were generally associated with viscosity-related satiety effects, whereas resistant starch was more frequently associated with gut fermentation, microbiota modulation, and short-chain fatty acid production. Mechanistic and metabolic evidence was predominantly derived from animal studies, and several human studies reported null findings. Overall, the findings suggest potential complementarity between glucomannan and resistant starch at the mechanistic level, but direct evidence supporting synergistic effects of their combined use remains limited.