A Type of Fiber May Have Weight Loss Benefits Similar to Ozempic

Research into the microbes that inhabit our digestive tract has sparked what many describe as a revolution in nutrition science.

Over the past few years, dietary fibre has been positioned as the “new protein”, with manufacturers adding it liberally to products to nourish the gut microbiome and support overall health. Yet evidence from a 2024 mouse study indicates that fibre supplements do not all deliver the same benefits.

Beta-glucan fibre and the gut microbiome: what the mouse study found

In the study, a type of fibre commonly found in oats and barley-beta-glucan-helped regulate blood sugar and supported weight loss in mice fed a high-fat diet.

Scientists from the University of Arizona (UA) and the University of Vienna reported that beta-glucan reduced body fat and overall body weight in mice within 18 weeks. By contrast, other fibres they assessed-including wheat dextrin, pectin, resistant starch, and cellulose-did not produce comparable reductions, even though they substantially altered the composition of the mice’s microbiomes when compared with mice receiving no fibre supplements.

Biomedical scientist Frank Duca (UA) highlighted the challenge in July last year: while fibre is clearly beneficial, there are many different types, and their effects are not interchangeable.

He explained that the aim was to identify which fibre might be most helpful for weight loss and improved glucose homeostasis, so the findings could guide the public and consumers, and also help inform decisions within the agricultural industry.

Why fibre types differ (soluble vs insoluble)

Dietary fibres provide a major fuel source for bacteria living in the gut. Despite that, fewer than 5% of people in the United States meet the commonly recommended intake of 25–30 g of fibre per day.

In response, fibre supplements and foods fortified with so-called “invisible fibre” have become increasingly popular. But because fibres vary so widely, choosing between them is not straightforward.

Some fibres-such as oat beta-glucans and wheat dextrin-are water-soluble, which generally makes them easier for gut microbes to ferment. Others-such as cellulose and resistant starch-are less soluble or insoluble, tending to bind with other materials and contribute to stool bulk.

Elizabeth Howard (UA) and colleagues noted that, until now, there had been no study examining the impact of multiple fibre types within a single cohort.

One cohort, several fibres: only beta-glucan boosted Ileibacterium

To address that gap, the researchers tested several fibre forms in the same group of mice. Only beta-glucan increased levels of Ileibacterium in the intestine-a bacterium that other mouse research has associated with weight loss.

Consistent with that link, well before the 10-week point, mice given beta-glucan showed lower body weight and reduced body fat compared with mice fed the other fibre types.

Butyrate, GLP-1, and links to insulin control

These results fit with another recent study led by Duca, in which rodents were fed barley flour rich in beta-glucan. Even though the animals continued to consume the same amount of high-fat food, their energy expenditure rose and they lost weight regardless.

A similar pattern appeared in the newer beta-glucan experiment. The mice also had higher concentrations of butyrate in their guts, a metabolite produced when microbes break down fibre.

Butyrate promotes the release of glucagon-like peptide-1 (GLP-1)-a naturally occurring protein that medicines such as Ozempic are designed to mimic in order to stimulate insulin release.

Duca said that a key part of dietary fibre’s benefit comes via GLP-1 and other gut peptides involved in appetite regulation and body-weight control. However, he and colleagues do not believe that mechanism explains everything; they suspect butyrate may confer additional advantages not directly tied to gut peptides, including supporting gut barrier integrity and influencing peripheral organs such as the liver.

What this might mean for people (and what it doesn’t yet prove)

Much more work is needed before these mouse results can be confidently applied to humans. Even so, the findings suggest that certain fibres may be better suited than others for weight management and insulin regulation.

In practical terms, beta-glucan is naturally present in widely available foods-particularly oats and barley-so increasing intake through everyday meals may be a more realistic strategy for many people than relying solely on supplements. In the UK, general guidance encourages aiming for around 30 g of fibre per day, which can be achieved by combining wholegrains, pulses, vegetables, fruit, nuts, and seeds.

It is also worth noting that “more fibre” is not always better if increased too quickly: sudden large increases can cause bloating or discomfort for some people. Gradual changes and adequate fluid intake often help, and anyone managing blood glucose or taking medication may wish to discuss significant dietary changes with a clinician.

The study was published in the Journal of Nutrition.

An earlier version of this article was published in July 2024.