Resistant Starch Diet is a Game Changer for Weight Loss and Diabetes Control

In a recent study published in the journal Natural metabolism, a team of scientists studied whether modulating the gut microbiome using dietary fiber supplementation in the form of resistant starch could help combat insulin resistance and weight loss and offer a pathway potential treatment for metabolic disorders.

Study: Consumption of resistant starch facilitates weight loss in humans by remodeling the gut microbiota. Image credit: Espace Sokor/Shutterstock

Background

Obesity has been classified as a global epidemic, with extensive research underway into strategies to reduce weight and prevent obesity. It contributes significantly to global mortality rates by increasing the risk of metabolic diseases such as diabetes, as well as the risk of cardiovascular diseases. Weight management and effective weight loss can reduce the risk of these diseases.

Increasing evidence indicates that the gut microbiome plays a central role in the regulation of human physiology and the development of various diseases. The composition and diversity of the gut microbiome are closely linked to glucose and fat metabolism and inflammation.

Additionally, although fecal microbiome transplantation has been used to establish healthy gut microbiome communities, the procedure has not yielded effective or long-term results. However, diet can be used to modulate the gut microbiome, and dietary interventions, alone or in conjunction with fecal microbiome transplantation, could potentially improve clinical outcomes.

About the study

In the current study, the team conducted a randomized crossover clinical trial involving overweight individuals to determine whether dietary supplementation with resistant starch had a positive impact on obesity and metabolic phenotypes. They also conducted metagenomic and metabolomic analyzes to understand how resistant starch affected the composition of the gut microbiome and its function.

Additionally, they studied antibiotic-treated mice that received gut microbiomes from human donors already altered by resistant starch supplementation to understand how gut microbiomes altered by resistant starch supplementation influence glucose metabolism and adiposity. . The metabolomic benefits offered by the gut microbiome altered by resistant starch supplements have also been explored.

Resistant starch cannot be broken down by amylase enzymes produced in humans, functioning like dietary fiber. During digestion, resistant starch is not broken down in the stomach or small intestine but moves to the large intestine or colon, where the gut microbiome ferments this dietary fiber. Studies in rodent models have shown decreased body fat and better metabolic results when the carbohydrate portion of their diet consists primarily of resistant starch.

The current clinical trial included overweight participants who did not have any chronic conditions, were not using any probiotics or antibiotics, and were not taking any medications that might impact their glucose metabolism. Participants were randomly assigned to the treatment or control group, with the treatment group receiving resistant starch in the form of high-amylose corn and the control group receiving amylopectin without resistant starch.

Starch was provided in sachets in powder form, and all participants in the treatment and control groups consumed an appropriate starch sachet twice daily before a balanced isoenergetic meal served three times daily. Since this was a crossover clinical trial, all participants underwent two eight-week interventions, one for the resistant starch treatment and one for the control treatment.

Results

The results showed that resistant starch supplementation achieved an average weight loss of approximately 2.8 kg and improved insulin resistance in overweight participants. The study also found that the beneficial effects of resistant starch supplementation were largely associated with changes in the composition of the gut microbiome.

The bacteria Bifidobacterium adolescentis was found to be associated with resistant starch supplementation in humans, and monocolonization of mice with this bacteria protected them from diet-induced obesity. Resistant starch impacted lipid and fat metabolism by reducing inflammation, restoring the intestinal barrier, and altering the bile acid profile.

The gut microbiota impacts host physiology via signaling metabolites, among which bile acids play an important role. Secondary bile acids, such as glycodeoxycholic acid, deoxycholic acid, glycocholic acid, and taurodeoxycholic acid, play an important role in improving insulin sensitivity and improving steatosis hepatic. The enzyme bile salt hydrolase carries out the deconjugation of secondary bile acids.

The study found that resistant starch supplementation decreased bile salt hydrolase production and increased secondary bile acid levels. The results were reciprocal in mice after their monocolonization with B.adolescent from humans who have undergone resistant starch supplementation.

Resistant starch (RS, 40 gd^-1) accompanied by an isoenergetic and balanced diet led to an obvious reduction in body weight and improvement in insulin sensitivity, as well as an alteration of metagenomics and metabolomics. Fecal microbiota transplantation (FMT) showed that the benefits of RS were associated with the remodeled composition of the gut microbiota. Monocolonization of mice with B. adolescentis, which closely correlated with the benefits of RS in human mice protected from diet-induced obesity. Mechanistically, RS-induced changes in gut microbiota influenced gut microbiome metabolites, reduced chronic low-grade inflammation by improving intestinal integrity, inhibited lipid absorption by modulating angiopoietin type 4 ( ANGPTL4) and enhanced the sensitivity of fibroblast growth factor 21. (FGF21) in adipose tissue. SPF, specific pathogen free; LPS, lipopolysaccharide; BCAA, branched chain amino acids; Erk1/2, extracellular signal-regulated kinase 1/2; FGFR1, fibroblast growth factor receptor 1. Created with BioRender.com.

Conclusions

In summary, the study found that resistant starch supplementation may facilitate weight loss by increasing the abundance of B.adolescent in the gut microbiome. It may also help improve insulin sensitivity through gut microbiome-induced changes in secondary bile acid levels and reduction of inflammation.