Scientifically Speaking | Resistant starch may change the weight loss game
A new study reveals that adding resistant starch, found in foods like plantains, beans, and whole grains, to our diet may lead to significant weight loss
Obesity is truly a global epidemic. A study published in the medical journal The Lancet last week found that one in eight individuals worldwide – amounting to over a billion people – are now classified as obese. Among children and adolescents, obesity rates have quadrupled since 1990, and among adults, rates have doubled.
This increase is not just confined to high-income nations, it is truly global. With the advent of ultra-processed foods, (which I talked about in a science column last month), lifestyles that lack exercise, and obesity and its related chronic illnesses like diabetes are increasing in countries like India that have growing economies.
A new class of weight loss drugs, known as GLP-1 drugs, show promise in treating obesity effectively. However, these drugs are in scarce supply and they’re no substitute for healthy living.
A recent small-scale study published in the scientific journal Nature Metabolism offers an approach that can become part of an effective plan to manage weight. This study shows that resistant starch – a type of carbohydrate which eludes quick digestion by human digestive enzymes but acts as a “prebiotic” that feeds beneficial gut bacteria – can help reduce weight.
Resistant starch is found in foods like plantains, beans, peas, lentils, whole grains like oats and barley, and cooked and cooled rice and potatoes. The cooking and cooling process can enhance the formation of resistant starch in foods such as rice and potatoes. Subsequent reheating does not seem to remove all the resistant starch found in these foods.
Huating Li and her team at Shanghai Jiao Tong University School of Medicine in China tested the ability of resistant starch to aid in weight loss with an eight-week investigation with 37 participants, 18–55 years categorised as overweight or obese, who were given sachets of resistant starch to consume twice daily before meals.
The participants were divided into two groups. One group consumed a diet supplemented with 40 grams of resistant starch every day for 8 weeks, while the other group received a controlled starch that didn't have the same properties. After those 8 weeks, everyone took a 4-week break from these special diets, allowing any effects of the starch to leave their system.
Then, the groups switched, allowing researchers to compare the effects of the resistant starch against the control starch within the same people. All the while, participants ate otherwise identical balanced meals per day.
During the phase in which participants consumed resistant starch, they experienced a decrease in body weight and fat stored around important internal organs. An interesting observation was that the participants had more fat in their stool, suggesting that their bodies were excreting more fat instead of storing it.
After testing stool samples, the scientists were able to see an increase in certain beneficial gut bacteria during the phase in which participants consumed added resistant starch. They found an increased presence of a bacterium known as "Bifidobacterium adolescentis", known for its ability to break down resistant starch.
The results were modest but promising. Those who consumed resistant starch lost an average of 2.8 kilograms, and this weight loss could not be replicated by eating ordinary starch. What’s more, resistant starch appears to moderate blood sugar spikes after eating, hinting at broader health benefits.
The scientists then introduced the beneficial gut bacteria from those consuming resistant starch to mice fed a high-fat diet. They saw immediate weight loss. The team also found changes in secondary bile acids, which are involved in fat digestion and branched short-chain fatty acids, which are important for gut health. Additionally, they found that resistant starch improves the integrity of the gut lining, which prevents harmful substances from leaking into the bloodstream and influences how the body manages fat storage and use.
Overall, the study suggests that consuming resistant starch has multiple benefits for people with extra weight, such as reducing body fat and improving gut health by changing the composition and activity of gut bacteria.
But there are certain caveats as well. For one, the study size was small. Another aspect was the weight regain observed during the break period for those who started on the resistant-starch diet. This isn’t surprising. Anyone who has lost weight knows the challenge of maintaining it. Currently, weight regain after discontinuing GLP-1 drugs seems to be one of the concerns with this obesity treatment.
In other words, it seems that in order to benefit from resistant starch (and quite possibly other prebiotics) you have to keep eating them. Adding more resistant starch might not be for everyone either. Before increasing the intake of resistant starch or any fibre, it's advisable to consult with a nutritionist or physician and to do so gradually while ensuring adequate water intake to minimize gastrointestinal side effects.
Lastly, diversity in fibre intake is beneficial, not just consuming one kind of carbohydrate like resistant starch.
That said, this is a truly exciting study. It not only shows the potential of resistant starch as a dietary intervention for better health but also leads the way for future studies that combine specific beneficial bacteria with the foods they eat. This could lead to a better understanding of the importance of maintaining beneficial gut microbes for maintaining long-term health.
Anirban Mahapatra is a scientist and author. His second popular science book, When The Drugs Don’t Work: The Hidden Pandemic That Could End Medicine, will be published this year. The views expressed are personal
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