Gut Microbiome May Shape Responses to GLP-1 Therapies in Obesity and Type 2 Diabetes
Key Takeaways:
- The gut microbiome may contribute to why people respond differently to GLP-1 receptor agonists, although causality remains unproven
- GLP-1 therapies and associated weight loss can alter gut microbial composition, but findings are inconsistent
- Dietary and behavioural changes during treatment are likely key drivers of microbiome shifts rather than direct drug effects
Emerging link between the gut microbiome and GLP-1 treatment response
A recent review published in the Canadian Journal of Physiology and Pharmacology highlights growing interest in the role of the gut microbiota in shaping responses to glucagon-like peptide-1 receptor agonists, commonly referred to as GLP-1 RAs. These medications are widely used in the management of people living with type 2 diabetes and those living with overweight or obesity.
The analysis suggests that gut microbial communities and their metabolites may contribute to the variability observed in treatment responses. At the same time, GLP-1 receptor agonists may themselves influence the composition of the gut microbiota. This bidirectional relationship positions the microbiome as both a potential contributor to treatment variability and a possible future target for more personalised metabolic therapies.
The gut microbiome as a regulator of metabolic health
There is increasing evidence that gut microbes play an active role in metabolic regulation. Preclinical studies using faecal microbiota transplantation have demonstrated that microbial communities can transfer traits such as glucose regulation and body mass. However, findings in human studies have been less consistent.
Despite the widespread use of GLP-1 receptor agonists, research exploring their interaction with the human gut microbiome remains limited. This is particularly notable given the considerable variation in how individuals respond to these treatments. Differences in microbial composition may partly explain this variability, although a definitive causal relationship has not yet been established.
In the review, researchers examined potential interactions between GLP-1 therapies, diet, gastrointestinal symptoms, body weight, and gut microbial composition.
Interactions between GLP-1 signalling and gut microbes
GLP-1 is a naturally occurring hormone that regulates appetite and blood glucose levels by binding to the GLP-1 receptor. It is released by L-cells in the intestine following nutrient intake. Because this release occurs in the lower intestine, GLP-1 operates in close proximity to the gut microbiota, raising the possibility of direct interaction.
Microbial metabolites such as bile acid derivatives and short-chain fatty acids can influence endogenous GLP-1 secretion and activity. These findings suggest that gut microbes may play a role in modulating GLP-1 signalling pathways. However, direct evidence demonstrating that microbial composition determines treatment response to GLP-1 receptor agonists in humans remains limited.
GLP-1 therapies may also indirectly affect the microbiome through changes in appetite, gastrointestinal motility, and dietary intake.
Clinical effectiveness of GLP-1 receptor agonists and variability in response
GLP-1-based therapies including liraglutide, semaglutide, and tirzepatide are now well established in the treatment of type 2 diabetes and obesity. Clinical trials have demonstrated significant weight loss outcomes:
- Tirzepatide – approximately 11.9–17.8% greater weight loss than placebo over 72 weeks
- Semaglutide – approximately 12.4% greater weight loss over 68 weeks
- Liraglutide – approximately 8.0% weight reduction compared with placebo over 56 weeks
Despite these results, individual responses vary widely. Differences in the gut microbiome have been proposed as one potential contributing factor, although this remains an area of ongoing investigation.
Microbiome changes associated with GLP-1 therapies
GLP-1 receptor agonists may influence gut microbial composition in people living with type 2 diabetes and obesity. Historically, obesity has been associated with a higher Firmicutes-to-Bacteroidetes ratio. Some studies suggest that weight loss is linked to increased microbial diversity and a greater abundance of beneficial genera such as Akkermansia.
Clinical observations include:
- Increased Akkermansia levels after six weeks of liraglutide therapy
- Increased levels of Bacteroidota, Actinobacteriota, and Proteobacteria following 12 weeks of semaglutide
- A reduction in Firmicutes in some cohorts
However, these findings are based on a limited number of heterogeneous studies. Many have involved people living with type 2 diabetes who were also taking other medications such as metformin, which is known to independently influence the gut microbiome.
GLP-1 receptor agonists, when combined with lifestyle modification, can lead to approximately 8–20% body weight reduction over several months to one year. Nevertheless, reported microbiome changes remain inconsistent. Some studies show increased diversity, while others report minimal or no significant changes.
Dietary changes during treatment and their microbiome impact
Evidence suggests that observed microbiome shifts may largely reflect downstream effects of weight loss and metabolic improvement rather than direct drug–microbiome interactions.
GLP-1 therapies are associated with changes in eating behaviour, including reduced appetite, increased satiety, and altered taste perception. People using these medications often improve their dietary patterns, with reduced consumption of refined grains, processed foods, beef, and sugar-sweetened beverages. Caloric intake may decrease by approximately 16–39%.
In 2025, organisations including The Obesity Society, American College of Lifestyle Medicine, American Society for Nutrition, and Obesity Medicine Association issued clinical guidance emphasising the importance of nutritional assessment and management of gastrointestinal side effects during GLP-1 therapy.
This guidance recommends prioritising nutrient-dense foods such as vegetables, fruits, whole grains, lean proteins, seeds, and nuts, while limiting refined carbohydrates, sugar-sweetened beverages, red and processed meats, fast foods, and highly processed snacks. Given the strong influence of diet on gut microbial composition, these dietary changes are likely to play a significant role in shaping the microbiome during treatment.
Future directions and research priorities
The review concludes that current evidence points towards behavioural and dietary changes, alongside weight loss, as the primary drivers of microbiome alterations observed during GLP-1 receptor agonist therapy.
However, the gut microbiome remains a promising area for future research. Microbiome profiling could eventually help predict treatment response more accurately in people living with obesity and type 2 diabetes.
Future studies should include:
- Larger and more diverse populations
- Longitudinal monitoring of microbiome changes
- Inclusion of people living with obesity who do not have diabetes
- Detailed tracking of dietary intake, gastrointestinal symptoms, and treatment adherence
Emerging therapies such as oral GLP-1 receptor agonists and new agents like orforglipron may offer further insight into direct interactions between medications and gut microbes, particularly as orally administered drugs come into direct contact with the gastrointestinal tract.
Understanding these relationships may ultimately support more personalised and effective approaches to obesity and diabetes care.
Read More
Big Breakfast Study Shows Protein Reduces Appetite While Fibre Supports Gut Microbiome Health
Key Takeaways:
- Within a calorie-restricted big-breakfast eating pattern, a higher-protein breakfast improved satiety, while a higher-fibre breakfast produced more favourable gut microbiota and short-chain fatty acid profiles.
- Both dietary approaches led to clinically meaningful short-term weight loss and improvements in metabolic markers, but with distinct physiological effects.
- Fibre-rich breakfasts were linked to greater abundance of beneficial butyrate-producing bacteria, whereas protein-rich breakfasts may better support appetite control and dietary adherence.
Background and rationale
A recent study published in the British Journal of Nutrition examined how breakfast composition influences appetite regulation, energy balance and markers of gut microbiota health when consumed as part of a calorie-restricted, big-breakfast weight-loss diet.
There is growing evidence that meal timing, in addition to dietary composition, plays an important role in healthy weight management. Previous research has shown that people who eat earlier in the day tend to lose more weight than those who eat later. Morning calorie intake has also been associated with improved blood glucose control and lower hunger levels compared with evening intake.
Larger breakfasts have been shown to improve appetite control, while late eating patterns have been linked to increased hunger and greater fat storage. Despite public health advice emphasising the importance of breakfast for weight management, relatively little is known about what people typically consume in the morning. Moreover, evidence explaining how meal timing, calorie distribution and macronutrient composition interact to influence appetite remains limited.
Study design and dietary interventions
The researchers used a randomised crossover design to compare two calorie-restricted weight-loss diets with identical big-breakfast calorie distribution but differing macronutrient profiles. The primary outcomes were appetite, energy balance and gut microbiota composition and metabolites, rather than clinical gastrointestinal outcomes.
Healthy adults with overweight or obesity, aged 18–75 years, were recruited. The protocol consisted of:
- a four-day ad libitum diet
- a four-day maintenance diet
- a 28-day high-fibre weight-loss diet or high-protein weight-loss diet
These phases were separated by a washout period, with participants acting as their own controls. Resting metabolic rate was measured by indirect calorimetry during screening.
The maintenance diet provided 15% of energy from protein, 55% from carbohydrate and 30% from fat, and was set at 1.5 times resting metabolic rate to maintain body weight. Both weight-loss diets were set at 100% of resting metabolic rate to induce a calorie deficit.
Participants consumed three meals per day, with 45% of daily calories at breakfast, 20% at lunch and 35% in the evening. Lunch intake was allowed ad libitum within the provided calorie allowance.
- High-fibre weight-loss diet – 50% carbohydrate, 15% protein and 35% fat, incorporating both soluble and insoluble fibre sources such as lentils, fava beans, buckwheat and wheat bran.
- High-protein weight-loss diet – 30% protein, 35% carbohydrate and 35% fat, using foods including fish, poultry, eggs, red meat and dairy.
Measurements and outcomes assessed
Body density, waist and hip circumference, resting metabolic rate, total body water and blood pressure were measured. The thermic effect of food was assessed every 30 minutes for four hours after breakfast. Subjective appetite was evaluated using visual analogue scales.
Blood samples collected after an overnight fast were used to assess glucose, lipid profile and insulin as metabolic biomarkers rather than clinical disease outcomes. Insulin and glucose values were used to calculate HOMA-IR, HOMA-β and the insulin-to-glucose ratio. Total body water was measured using deuterium dilution, and faecal samples were collected to analyse gut microbiota composition.
Weight loss, energy expenditure and metabolic markers
Nineteen participants completed the study, including two women. The mean age was 57.4 years and the mean body mass index was 33.3 kg/m², indicating a predominantly male cohort and limiting generalisability to broader populations.
Energy intake did not differ significantly between the two weight-loss diets. Average weight loss was 4.87 kg with the high-fibre diet and 3.87 kg with the high-protein diet. Both diets significantly reduced fat mass and fat-free mass compared with the maintenance diet, although loss of fat-free mass was greater with the high-fibre approach.
Total body water was reduced following the high-fibre diet but not after the high-protein diet. Waist and hip circumferences, as well as waist-to-hip ratio, were significantly reduced with both weight-loss diets compared with the maintenance diet.
The high-protein breakfast maintained postprandial satiety, whereas the high-fibre breakfast was associated with reduced satiety after meals. Resting metabolic rate declined significantly after both weight-loss diets. The thermic effect of food was lower following the high-fibre diet than after the high-protein or maintenance meals.
Both weight-loss diets improved lipid profiles relative to baseline, with no significant difference between the two approaches. Fasting and postprandial glucose levels were reduced by around 10% following the high-fibre diet and by 8–7% following the high-protein diet compared with the maintenance diet. Fasting insulin, HOMA-IR and the insulin-to-glucose ratio were significantly lower after both weight-loss diets.
HOMA-β decreased significantly more after the high-protein diet than after the maintenance diet, with no significant change observed after the high-fibre diet.
Gut microbiota composition and short-chain fatty acids
Total bacterial load in faecal samples did not differ significantly between the two weight-loss diets. However, microbial diversity was lower following the high-protein diet compared with the high-fibre diet.
Distinct differences in microbiota composition were observed between the dietary patterns, although individual variation remained a major determinant of microbiota profiles and diet explained only part of the observed variability.
The high-fibre diet was associated with a greater abundance of butyrate-producing bacteria, including Anaerostipes hadrus, Roseburia faecis and Faecalibacterium prausnitzii. At the genus level, Bifidobacterium, Faecalibacterium and Roseburia were linked to the high-fibre diet, while Streptococcus was associated with the high-protein diet.
Total short-chain fatty acids and key faecal short-chain fatty acids, including acetate, butyrate and propionate, were significantly lower with the high-protein diet compared with the high-fibre diet.
Interpretation and clinical implications
Overall, the findings suggest that within a calorie-restricted big-breakfast eating pattern, breakfast composition meaningfully influences short-term weight loss, metabolic health markers and gut microbiota characteristics.
Both dietary approaches led to significant weight reduction and metabolic improvements. The high-protein breakfast produced greater satiation, which may support long-term adherence in some people. In contrast, the high-fibre breakfast promoted a more favourable gut microbiota profile and higher short-chain fatty acid production, which may be beneficial for long-term gut health, although this was inferred from microbial and metabolic markers rather than direct clinical outcomes.
The authors emphasised that longer-term studies are needed to determine whether these differences are sustained over time and how they translate into long-term health outcomes.
Read More
Maternal Obesity Linked to Early Changes in Infant Gut Microbiome, Study Suggests
Key Takeaways:
- Infants born to mothers with obesity show distinct differences in gut bacteria during the first six months of life, including reduced microbial diversity.
- These early microbial changes are associated with pathways linked to fat metabolism, particularly in the first three months after birth.
- Researchers suggest that early-life interventions targeting the gut microbiome may help reduce longer-term metabolic risks for children.
Maternal obesity and the infant gut microbiome
Babies born to mothers with obesity may begin life with a markedly different gut microbiome, a factor that could influence their metabolism and long-term health, according to new research from Nazarbayev University (NU).
The study, led by researchers Almagul Kushugulova and Samat Kozhakhmetov, explored how maternal obesity may shape the early development of the gut microbiome in infants. The research team followed 24 mothers and their babies from birth to six months of age, analysing stool samples using advanced DNA sequencing techniques.
By comparing infants born to mothers with obesity with those born to mothers without obesity, the researchers identified clear differences in the composition and diversity of gut bacteria during early life.
Reduced microbial diversity and altered metabolic pathways
The analysis showed that infants of mothers with obesity had significantly lower gut microbial diversity. In addition, these infants had a higher abundance of bacterial species associated with fat metabolism.
These differences were most pronounced during the first three months of life, a period widely recognised as critical for the establishment of the gut microbiome and for metabolic programming.
“During the first three months of life, we observed what appears to be a shift in how gut bacteria process nutrients – with a tendency toward fat storage pathways rather than breaking down carbohydrates for energy,” Kozhakhmetov explained.
He noted that this early metabolic pattern may have implications for how energy balance is regulated later in life.
Opportunities for early intervention
The researchers suggest that their findings open the door to preventive strategies during infancy. Kozhakhmetov highlighted that understanding these early microbial shifts could inform interventions aimed at promoting healthier metabolic outcomes.
This discovery, he said, “opens up possibilities for early intervention”, including approaches such as targeted probiotics or tailored dietary guidance designed to support a more balanced gut microbiome and potentially reduce future metabolic risk.
Beyond metabolism – immune and appetite regulation
The implications of the findings may extend beyond metabolism alone. The researchers propose that maternal obesity could also influence immune system development and appetite regulation in children through microbial transmission.
“We tend to think that we only pass on our genes to our children. But our research suggests that we may also pass on our bacteria – and the type of bacteria a child inherits could have important effects on their long-term health, potentially influencing their health trajectory as they grow,” Kushugulova said.
This perspective reinforces the idea that early-life exposures play a significant role in shaping health across the life course.
Placing the findings in context
The study, published in the journal Biomedicines, adds to a growing body of research highlighting the importance of the early-life microbiome. Previous studies have linked maternal weight status and gut dysbiosis to disrupted nutrient metabolism, inflammation, and changes in immune, metabolic, or neurodevelopmental outcomes in children.
As obesity during pregnancy becomes increasingly common worldwide, the authors argue that maternal health should be viewed as a key determinant not only of pregnancy outcomes, but also of a child’s longer-term metabolic health.
Implications for future research and practice
The researchers conclude that interventions targeting the gut microbiota during early infancy may represent a promising avenue for reducing health risks associated with maternal obesity. Further research will be needed to determine which strategies are most effective, when they should be implemented, and how they can be integrated into routine maternal and child healthcare.
Taken together, the findings underline the importance of addressing obesity before and during pregnancy, while also highlighting the potential of microbiome-focused approaches to support healthier outcomes for future generations.
CCH insight:
Evidence for the role of the gut microbiome in obesity and metabolic health continues to grow. This study is ground-breaking in demonstrating that maternal obesity influences the new-born child’s microbiome, potentially priming the child for health challenges later in life right from their first few weeks of life. On the positive side, this offers the potential to identify babies at risk of metabolic diseases from a very early stage of life, and also the opportunity for early interventions though diet, pre- and probiotics.
Read More