Latest insights on Ozempic and the gut

As GLP-1 receptor agonists like semaglutide (Ozempic, Wegovy) become more widely prescribed for type 2 diabetes and weight management, general practitioners are increasingly likely to encounter patients experiencing gut-related side effects. Beyond common symptoms like nausea or reflux, these medications offer a valuable opportunity for patients to adopt sustainable dietary changes.

GI side effects: Common but manageable

GLP-1 medications delay gastric emptying and increase satiety, helping reduce overeating but often causing gastrointestinal symptoms, including:

• Upper GI: nausea and vomiting¹
• Lower GI: constipation and diarrhoea¹

These side effects are usually dose-dependent, most frequent during initiation or dose escalation, and typically mild to moderate. Nausea and diarrhoea often improve over time, while constipation may persist.¹

Encouraging smaller, more frequent meals can ease nausea, and increasing fibre and fluid intake can relieve constipation. GPs play a crucial role in anticipating and managing these side effects effectively.

GLP-1 and the gut microbiota

The gut microbiome plays a central role in metabolism, inflammation, and digestive health. Emerging evidence suggests GLP-1 therapy also influences gut microbial composition.

A 2024 systematic review of 38 animal and human studies found that GLP-1 medications significantly affect gut microbiota diversity and composition²:

• Liraglutide: promotes growth of beneficial genera linked to improved metabolic health
• Dulaglutide: increases Bacteroides, Akkermansia, and Ruminococcus, genera associated with better gut and metabolic outcomes
• Semaglutide: increases Akkermansia muciniphila, a beneficial bacterium, but may reduce overall microbial diversity; effects vary by population and study design

These findings highlight a complex but potentially positive interaction between GLP-1 medications and the gut microbiome, underscoring the importance of dietary strategies that support microbial diversity.

Clinical nutrition tips with a gut focus

Given the reduced appetite and altered gut motility common with GLP-1 therapy, small nutritional adjustments can make a big difference. Instead of focusing on restrictions, GPs can encourage patients to focus on habits that nurture gut and metabolic health:

• Fibre-rich foods (whole grains, legumes, vegetables): promote bowel regularity and microbial diversity
• Hydration: supports constipation management and reduces nausea
• Nutrient-dense, whole foods: prioritise quality over quantity, especially when appetite is low

GLP-1 receptor agonists provide a unique window to build lasting healthy habits. With appropriate support, patients can lose weight, improve glycemic control, and enhance gut and metabolic health while maintaining adequate nutrient intake and adherence.

GPs can support this process by addressing gut symptoms early, offering practical symptom relief, and encouraging gut-friendly eating aligned with patient preferences. Referral to a dietitian is advised when symptoms persist, food aversions arise, or pre-existing gut conditions or additional support needs are present.

– Sarah Marko, Accredited Practising Dietitian

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References

1. Wharton, S., Davies, M., Dicker, D., Lingvay, I., Mosenzon, O., Rubino, D. M., & Pedersen, S. D. (2021). Managing the gastrointestinal side effects of GLP-1 receptor agonists in obesity: recommendations for clinical practice. Postgraduate Medicine, 134(1), 14–19. https://doi.org/10.1080/00325481.2021.2002616
2. Gofron, K. K., Wasilewski, A., & Małgorzewicz, S. (2025). Effects of GLP-1 Analogues and Agonists on the Gut Microbiota: A Systematic Review. Nutrients, 17(8), 1303. https://doi.org/10.3390/nu17081303