Weight loss injections such as Mounjaro and Ozempic are transforming obesity and type 2 diabetes treatment. They are highly effective for weight loss but they also often come with unpleasant gastrointestinal side effects, including bloating, nausea, and constipation.
In this article, we’ll explore the link between GLP-1 agonists and bloating, and whether dietary changes and gut health supplements containing fibre, prebiotics, and probiotics may help ease some of the distressing symptoms.

 

What is Mounjaro and how does it work?

Mounjaro or tirzepatide is a dual agonist for the body’s natural peptides GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide). It works to regulate the blood sugar, suppress appetite, and promote weight loss.
However, Mounjaro like other weight loss injections such as semaglutide, sold as Ozempic and Wegovy often slows down the rate at which the stomach empties. That keeps you fuller for longer, reduces hunger and supports weight loss but it can also cause:

•    Bloating
•    Constipation
•    Nausea
•    Flatulence

According to a 2022 study in The New England Journal of Medicine, gastrointestinal side effects were among the most common adverse events in the clinical trials for tirzepatide or Mounjaro.

 

Why does bloating occur with weight loss injections?

GLP-1 receptor agonists like Mounjaro work by delaying stomach emptying- a process known as gastric stasis. This effect can cause trapped gas, pressure, and discomfort. The medications can also reduce gut motility, contributing to constipation which can also cause bloating.

The altered digestion can also affect the gut microbiome, the balance of ‘good’ and ‘bad’ bacteria in your bowels. An imbalanced microbiome can potentially increase fermentation in the gut and drive intestinal gas production  especially when dietary fibre or carbohydrates aren’t well tolerated.

 

Lifestyle tips to manage bloating on Mounjaro

Bloating can be a distressing symptom when you’re taking weight loss injections. However, there are ways to ease your discomfort:

Eat smaller, slower meals

Mounjaro slows gastric emptying, so eating large meals quickly can lead to a heavy, bloated feeling. Eat slowly, chew thoroughly, and stop when you feel comfortably full. Aim for smaller, more frequent meals so you get the nourishment you need.

Cut out gas-producing foods

Certain foods like beans, lentils, broccoli, onions, and cabbage can cause bloating due to fermentation in the gut. Try and reduce your intake of cruciferous vegetables and legumes and instead try low-FODMAP alternatives like courgettes, spinach, and carrots. When your symptoms are stable, try reintroducing them slowly to assess your tolerance.

Avoid fizzy drinks and chewing gum

Fizzy drinks and chewing gum can increase the amount of air you swallow and make you gassy. Swap them for still water or herbal teas to beat the bloat.

Increase fibre gradually

Fibre supports healthy digestion, but increasing it too quickly can lead to gas and bloating. Slowly build up fibre from wholegrains, fruits, and vegetables, drink plenty of water to support digestion and consider a prebiotic fibre like inulin in small amounts at first.

Cut back on fatty and fried foods

High-fat meals take longer to digest and can increase feelings of bloating. Choose lean protein sources like chicken, fish, eggs, or tofu. Try to grill, bake, or steam instead of frying and limit heavy, creamy sauces.

Limit sugar alcohols and sweeteners

Sorbitol, mannitol, and xylitol are common in sugar-free products- they’re low in calories but they’re also poorly absorbed and can ferment in the gut, producing gas.
Check labels on protein bars, gums, and sugar-free products and instead choose naturally sweet options like berries or dark chocolate.

Stay hydrated

Hydration helps prevent constipation, which can worsen bloating. Drink at least 6–8 glasses of fluid daily to help fibre move through your bowel.

Keep a diary

Track your symptoms with a bloating diary, noting any potential triggers.

Move it

Movement supports digestion. Go for a light walk after meals to aid the digestive process and reduce bloating.

If bloating persists on Mounjaro, speak to your GP or pharmacist. Sometimes adjusting the dose or timing can help, and a dietitian can tailor advice to your individual gut tolerance.

 

Could gut supplements help?

A well-designed supplement containing fibre, prebiotics, and probiotics may help support digestion and reduce bloating associated with weight loss injections.

Fibre first

Fibre can keep your bowels regular without creating excess gas- but not all fibre is equal. When choosing a supplement, it’s important to include low-FODMAP soluble fibres, such as:

•    Psyllium husk – well tolerated and shown to improve stool consistency without excessive fermentation

•    Partially hydrolysed guar gum (PHGG) – gentle on the gut and supports beneficial bacteria

•    Oat fibre-The British Dietetic Association (BDA) recommends oats as a gut-friendly option for most people with IBS—though individual tolerance varies.

When introduced gradually, these fibres help form soft, bulky stools and can reduce constipation without worsening bloating.

A 2021 review in the British Journal of Nutrition found psyllium effective in treating constipation with minimal gas production.

Prebiotics: Fuel for the good bacteria

Prebiotics are fermentable fibres that feed beneficial gut bacteria. Examples include Inulin, FOS (fructooligosaccharides) and GOS (galactooligosaccharides) and can improve and balance your microbiome. 

However, take care, high doses of inulin or FOS may worsen bloating in sensitive individuals, particularly during GLP-1 therapy. The most common side effects of gas, bloating, diarrhoea, constipation, and cramps tend to be more severe with high doses of inulin (more than 30 grams). Nixi contains 640mg of Inulin per fibre shot.

 

Probiotics: Rebalancing your microbiome

Probiotics help restore the balance of bacteria in your bowels and may reduce gas production and inflammation. 

Each shot of Nixi includes a billion CFU each of Lactobacillus Acidophilus and Bifidobacterium Bifidum. When taken regularly, these can help support a balanced gut microbiome, regulate your bowel movements and relieve symptoms of uncomfortable and distressing conditions including irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

https://pmc.ncbi.nlm.nih.gov/articles/PMC4372813/

When to speak to a healthcare professional

Bloating can be an indication of an underlying health problem. See your doctor if your bloating is severe, persistent, or accompanied by:
•    Vomiting

•    Weight loss

•    Abdominal pain

•    Rectal bleeding

•    Change in bowel habit

•    Persistent abdominal distension

 

In summary

Weight loss injections (WLI) like Mounjaro are powerful tools in the treatment of obesity and type 2 diabetes, but they can disrupt gut function and cause bloating.

Taken regularly a supplement like Nixi containing gentle fibre, probiotics and prebiotics can help promote regular bowel movements, support a healthy microbiome and help manage gas and bloating by reducing fermentation and supporting better digestion.

CAUTION: Increasing fibre can increase wind and bloating. Always introduce gut supplements gradually and see how your body responds before increasing to a daily dose. Consult your GP or pharmacist before use—especially if you are taking other medications.

 

Find out more:

Check out these sources and links to take a deeper dive into bloating and WLI and explore the references we used in researching and writing this article.

•    Jastreboff AM et al., NEJM, 2022 – Tirzepatide in Obesity
•    British Journal of Nutrition, 2021 – Psyllium and gastrointestinal tolerance
•    National Institute for Health and Care Excellence (NICE) – GLP-1 guidance
•    Slavin J, Advances in Nutrition, 2013 – Fibre and the microbiota
•    Hill C et al., Nutrients, 2020 – Probiotics in bloating and IBS
•    https://pmc.ncbi.nlm.nih.gov/articles/PMC4372813/