Resistant starch intake facilitates weight loss in humans by reshaping the gut microbiota

Randomized crossover trial in adults with overweight or obesity (BMI ≥ 24 kg/m2) in Shanghai, China. Participants were generally healthy, lightly active or sedentary, and followed a controlled isoenergetic background diet during the study. The resistant starch group included 37 participants.

Adults in the resistant starch arm received 40 g/day of type 2 resistant starch (HAM-RS2; maize resistant starch) for 8 weeks by mouth. The powder was provided in pre-packaged sachets, taken as one sachet twice daily 10 to 15 minutes before meals and mixed with 300 ml water. The intervention was compared with corn starch in a randomized crossover trial.

Resistant starch produced clinically meaningful weight loss and improved metabolic markers versus corn starch. Body weight decreased by a net -2.81 kg (95% CI -3.55 to -2.07; P < 0.001), with reductions in fat mass, waist circumference, visceral fat area, and subcutaneous fat area. Insulin sensitivity improved, with glucose infusion rate increasing significantly after resistant starch (P = 0.025; median increase 1.05 mg kg -1 min -1, 0.15 to 2.10), and inflammatory markers TNFα and IL-1β decreased. Adiponectin increased and FGF21 decreased, with no reported adverse gastrointestinal effects. Overall, the benefit was linked to gut microbiota remodeling, supporting resistant starch as a practical dietary approach for obesity management.

The trial was small, single-center, and short term, so durability of weight loss and metabolic effects is unknown. Participants were limited to adults with overweight or obesity in Shanghai, which restricts generalizability. Mechanistic conclusions about microbiota-mediated causality are supported by animal experiments but remain partly indirect in humans.