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Diet rich in resistant starch may help with weight loss, according to a new study. Image credit: Crissy Mitchell/Stocksy.
  • Researchers have unveiled a potential new strategy for treating obesity and metabolic diseases through dietary intervention.
  • By incorporating resistant starch into the diets of individuals with overweight, scientists observed significant weight loss and improvements in insulin sensitivity, highlighting the influential role of the gut microbiome in overall health.
  • This research not only underscores the global urgency of addressing obesity but also suggests that modulating the gut microbiome with specific dietary components could offer a promising avenue for preventive and therapeutic measures against metabolic disorders.

Obesity is now recognised as a worldwide health crisis, contributing to global mortality by elevating the risk of metabolic disorders like diabetes and increasing the likelihood of cardiovascular disease.

Losing weight through diet and exercise is an important measure to prevent or reduce obesity.

Research increasingly shows the gut microbiota’s link to how the body handles glucose and fats and also how it affects inflammation.

While fecal microbiota transplantation — which aims to induce the proliferation of “good” gut bacteria — has seen mixed success in promoting a healthy gut, dietary modifications have proven to impact the microbiota positively, suggesting that diet-based approaches, alone or in combination with transplantation, could improve health outcomes.

Resistant starch is not digestible by human-produced amylase enzymes, and acts as a form of dietary fibre.

It passes through the stomach and small intestine undigested, reaching the large intestine or colon, where it is fermented by the gut microbiota.

Studies in rodents have demonstrated that diets high in resistant starch can lead to reduced body fat and improved metabolic health.

In a new study, published in Nature Metabolism, researchers modified the gut microbiota of human participants by increasing dietary fibre to investigate how it might help manage insulin resistance while also reducing weight.

Researchers conducted a randomised, crossover clinical trial to assess the impact of resistant starch, sourced from high-amylose maize, on obesity and metabolic health.

Participants, not on probiotics, antibiotics or treatments affecting glucose metabolism, were divided into a treatment group receiving resistant starch and a control group receiving amylopectin.

The trial involved consuming the assigned starch in powdered form twice daily before meals over two eight-week phases, allowing for direct comparison between the effects of resistant starch and the control.

The research also investigated how gut microbiota, modified by resistant starch supplementation. affect glucose metabolism and fat accumulation to understand the metabolic benefits.

The findings indicated that adding resistant starch to the diet resulted in an average weight reduction of approximately 2.8 kilograms (kg) and enhanced insulin sensitivity among individuals with overweight.

Researchers observed that the positive effects of resistant starch on health were primarily due to alterations in the composition of the gut microbiota.

Specifically, the presence of the bacterium Bifidobacterium adolescentis was significantly linked to the intake of resistant starch in humans, and introducing this bacterium alone to mice safeguarded them against obesity caused by their diet.

The research concluded that adding resistant starch to the diet leads to weight reduction and enhances insulin sensitivity, primarily by boosting the presence of B. adolescentis in the gut microbiota.

Three experts, not involved in this research, spoke to Medical News Today about its findings.

Dr. Mir Ali, bariatric surgeon and medical director of Memorial Care Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA, said that this paper “highlights the importance of the gut microbiota and the role it plays, not just for weight loss, but overall health as well.”

Kelsey Costa, MS, RDN, a registered dietitian nutritionist and founder of the Dietitian Insights collaborative, agreed, noting that “the research surrounding resistant starch is a burgeoning area of interest in the nutritional science field.”

“The weight loss observed in this study is linked to alterations in the composition of gut microbiota, specifically, the increase of Bifidobacterium adolescentis, which was significantly associated with obesity reduction in the participants and has shown protective effects against diet-induced obesity in male mice,” Costa explained.

“As we continue to unravel the multifaceted relationships between diet, gut microbiota, and human health, the potential of resistant starch as a functional food ingredient for obesity management and metabolic health improvement remains an exciting and valuable area of exploration.”

– Kelsey Costa

Megan Hilbert, MS, RDN, a registered dietitian specialising in gut health nutrition, from Top Nutrition Coaching, said that, “based on this study’s findings, resistant starch proved to be an effective way to reduce obesity and well as insulin sensitivity in participants who received the resistant starch intervention.”

Dr. Ali noted several implications of this research, for example, by “re-establishing a healthy gut microbiota, it could help facilitate weight loss.”

“Of course, there is much more research that needs to be done in this area,” Dr. Ali said. “Also, the intestinal microbiota is not the only factor that affects a patient’s weight and overall health.”

“Patients need to understand that there are many components to a healthy weight loss plan and maintenance of weight and health. Genetics, lifestyle, exercise and healthy gut microbiome all play a role, but the majority of weight loss is due to the change in diet.”

– Dr. Mir Ali

Hilbert noted how clinicians “can thankfully easily apply these findings to our work with our patients by educating these individuals more on how to include foods high in resistant starch.”

“Resistant starch occurs naturally in many foods like oats, cooked and cooled rice, grains like sorghum and barley, beans and legumes like black beans, peas, pinto beans, etc, raw potato starch or cooked and cooled potatoes, green bananas, and more,” she explained.

“It’s also possible to supplement with resistant starch, but I recommend trying to get resistant starch through whole foods to get health benefits from the other aspects of these foods — vitamins, minerals, protein, prebiotics, other fibers,” Hilbert suggested.

“When adding in more resistant starch, I usually advise people to start slow and allow the gut microbiota to adapt to changes if they aren’t used to eating much fiber or resistant starch to avoid any unpleasant side effects,” she said.

Costa explained that “resistant starch is distinguished as a distinct dietary fiber that bypasses digestion in the small intestine and undergoes fermentation in the colon, where it interacts with gut microbiota, potentially leading to a significant reduction in body fat based on [the findings from] animal studies.”

However, “while rodent studies have highlighted the potential for resistant starch to influence metabolic outcomes favorably, previous human studies have been limited and observed little body weight alterations following resistant starch supplementation, suggesting variable effects on human metabolic health,” Costa said.

Costa explained that research indicates that the fat content in diets affects the fermentation and health benefits of resistant starch.

High-fat diets can negatively impact gut microbiota, hindering resistant starch’s benefits, while low-fat diets enhance its fermentation, promoting metabolic health.

This highlights the importance of whole, plant-based foods for optimal resistant starch intake and health outcomes.

“The findings bolster the argument for a dietary shift towards plant-based nutrition, highlighting the inherent health benefits and the role of resistant starch in fostering a healthier gut microbiome and promoting optimal metabolic health.”

– Kelsey Costa