Could a gut microbe help reduce weight regain after dieting? New study suggests it might

Losing weight is hard. Keeping it off is often even harder.

Research has shown that most people who intentionally lose weight regain at least some of it within a few years. This is often attributed to lack of “willpower”, but the evidence actually shows that after we lose weight, the body undergoes a range of biological changes that encourage weight regain. This includes increased hunger, changes in metabolism and shifts in hormones involved in appetite regulation.

Even people who lose weight using a GLP-1 drug find it difficult to maintain their weight loss once treatment stops.

For this reason, finding ways to help people maintain weight loss is a key area of research.

A new study published in Nature Medicine suggests that one particular gut microbe may help to prevent weight regain.

The bacterium, called Akkermansia muciniphila, is an abundant species in the human gut microbiome. It lives in the mucus layer that lines the gut. It’s able to feed on mucin (the proteins and sugars that make up this mucus), and is thought to play a role in maintaining the gut’s protective barrier and can also influence metabolism.

Akkermansia muciniphila has attracted attention in microbiome research in recent years due to its association with improved health outcomes across multiple diseases.

Studies in humans have shown that higher levels of Akkermansia muciniphila are linked with better metabolic health, including improved blood sugar control, which reduces the risk of developing health problems such as type 2 diabetes. On the other hand, lower levels of Akkermansia muciniphila are observed in people with obesity and type 2 diabetes.

This recent study investigated whether supplementing people with Akkermansia muciniphila after weight loss could help limit subsequent weight regain.

The trial involved 90 adults who were overweight or obese. Participants followed a low-energy diet for eight weeks. This consisted of meal replacement soups and shakes totalling 800-900 calories per day.

After this phase, participants who lost at least 8% of their body weight were then randomly assigned to receive either a placebo or daily supplements containing pasteurised Akkermansia muciniphila for 24 weeks. They were also instructed to follow a healthy diet that aligned with Dutch dietary guidelines, but were told they could eat as much or little as they wanted.

This study did not use live Akkermansia muciniphila bacteria. Instead, they used a pasteurised version (meaning the bacteria had been heat-treated and were no longer alive). This may sound counterintuitive, but previous research suggests that some of the beneficial effects of probiotics, including A muciniphila, may come from components of the bacterial cell rather than live microbes. Pasteurisation may even enhance the microbe’s effects.

By the end of the study, the group receiving Akkermansia muciniphila had regained significantly less weight than the placebo group. On average, those taking the supplement regained around 1.2kg, compared with 3.2kg in the placebo group. This suggests that supplementation slowed, but did not fully prevent, weight regain after initial weight loss.

The researchers also observed some improvements in some cardiometabolic markers, including improved insulin sensitivity (meaning the body is responding to insulin more effectively) in the supplemented group.

The gut microbiome and body weight

The microbiome is highly complex. It is influenced by diet, exercise, sleep, medications and many other factors. As a result, microbiome-based therapies are unlikely to be simple, one-size-fits-all solutions.

Although the findings are encouraging, the study was relatively small and only lasted six months after the initial weight-loss phase. We still do not know whether the effects would continue over longer periods.

There are also questions about who is most likely to benefit, as participants with lower baseline gut levels of Akkermansia appeared to show greater cardiometabolic improvements. This highlights a broader challenge in microbiome science: people’s gut microbiomes vary enormously, and treatments that work well for one person may have little effect in another.

The study also involved substantial dietary intervention and support, including the provision of a meal replacement plan for the initial weight loss, and support from dietitians throughout the entire study period. So the microbe was not tested in isolation from lifestyle changes, nor should it be viewed as a substitute for them.

It’s also worth noting that several authors declared links to the company producing the supplement used in the trial. While such collaborations are common in translational research (studies which test lab findings in real people to understand health benefits), independent studies will be important to confirm and build on these findings.

That said, the microbiome is still a fascinating and increasingly important area of research with clear links to many aspects of human health. Our understanding of it is still developing. However, research so far shows that the microbiome plays key roles in metabolism and immunity, meaning it can influence both health and the development of disease.

Many probiotic supplements currently marketed to consumers have limited evidence behind them. Although studies like this suggest that carefully targeted microbiome therapies may have potential to eventually be used as part of weight-maintenance strategies, much more research is needed.

It may even be possible to support and increase Akkermansia muciniphila without supplementation. Diet plays an important role in shaping the microbiome. Diets rich in fibre, particularly prebiotic fibres (a type of dietary fibre that feeds beneficial gut bacteria), can help create an environment in which beneficial bacteria, including Akkermansia muciniphila, can thrive.

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These fibres are found in foods such as onions, garlic, leeks, asparagus and many whole grains. Plant foods high in polyphenols (naturally occurring plant compounds that can protect cells against damage and inflammation) – such as berries and grapes – may also promote its growth.

For now, the findings from this study add to growing evidence that body weight is influenced by a complex interplay of biological, environmental and behavioural factors. They also contribute to an increasingly clear picture of the gut microbiome as an important regulator of metabolism and health.