Eating Resistant Starch Can Lead to Weight Loss, Study Finds

A form of dietary fiber found in foods such as raw oats and beans may help with weight loss, according to a new small study.

A diet containing high amounts of resistant starch, a form of dietary fiber found in whole grain foods and legumes, may lead to improvement in the gut microbiome in people with obesity, ultimately leading to weight loss and other positive health benefits.

Published in Nature Metabolism this week, the findings suggest that a diet rich in resistant starch may also result in improved glucose tolerance and insulin sensitivity, potentially reducing the risks of developing type 2 diabetes and cardiovascular diseases in overweight and obese individuals.

Resistant starch is a type of carbohydrate that cannot be digested in the small intestine and instead ferments in the large intestine, acting as a probiotic. As a result, it increases the amount of good bacteria in the gut and doesn’t raise glucose levels in the same way as ordinary starches.

Plantains, green bananas, beans, peas, lentils, and whole grains including oats and barley, all contain resistant starch. Heat can also change the amount of resistant starch in some foods. While oats, green bananas, and plantains lose some of their resistant starch when cooked, cooked rice and potatoes that have been cooled down develop into resistant starch throughout the cooling process.

An international team of researchers conducted a small clinical trial by giving 37 overweight and obese participants a resistant starch supplement in the form of a powder dissolved in water twice a day for a period of eight weeks. They were also given three healthy meals a day. For an additional eight weeks, the participants were instead given a supplement of ordinary starch.

Following the first eight-week period, participants lost an average of 2.8 kilograms. No weight loss was observed during the second period of consuming the ordinary starch supplement.

The resistant starch also resulted in a smaller rise in blood sugar following meals, and stool samples from participants revealed an increase in good gut bacteria. Researchers then transferred this good bacteria into mice eating a diet high in fat, and this appeared to help them lose weight, too.

An additional mouse experiment revealed that a particular bacterial species within the gut microbiota, called Bifidobacterium adolescentis, is required to prevent the intestine absorption of fat and protect against obesity.

"Using analytical methods, we were able to show that the composition and metabolic output of the study participants' gut microbiome had changed into a favorable direction for the host,” said Gianni Panagiotou, a professor at Friedrich Schiller University Jena and one of the study authors, in a news release. “Our study will provide a practical approach to treat obesity and its related metabolic disorders by resistant starch.”