Ozempic, Mounjaro, and Wegovy are reshaping the world of weight loss. These medications, known as GLP-1 receptor agonist medications, can lead to remarkable weight reductions, marking the start of a new era in obesity treatment. With all the hype, you’d be forgiven for thinking that the way you eat and move has been replaced with an injection. In reality, diet and lifestyle still matter… perhaps more than ever.
This post explores how these drugs work, who should or shouldn’t use them, what a healthy GLP-1 weight-loss diet really looks like… and why food still holds the power.
When you eat, your body naturally releases hormones that help you regulate your appetite and blood sugar. One of these is GLP-1 (glucagon-like peptide-1) which helps control your blood sugar, slows down how quickly food leaves your stomach, and tells your brain that you have had enough to eat (1).
GLP-1 medications mimic this natural hormone, meaning that when you take it you feel full sooner, feel less hungry between meals, and experience fewer cravings and steadier blood sugar levels.
Here are some of the currently available forms of GLP-1 medication:
So far, so scientific… but what does this actually mean for real people trying to lose weight?
In the SURMOUNT-1 clinical trial, people taking the highest dose of tirzepatide for 72 weeks, alongside healthy lifestyle changes, lost an average of around 21% of their body weight (3).
These results are impressive, but nutrition and lifestyle remain an important part of treatment. Clinical trials of these medications have generally included support with diet and physical activity, while current clinical guidance recommends medication alongside appropriate nutritional, physical activity and behavioural support (4,5).
There is also increasing recognition that obesity is a chronic, relapsing condition and these medications may need to be used long term for many people. Studies in which semaglutide or tirzepatide have been withdrawn show that substantial weight regain is common after stopping treatment (6,7).
GLP-1 medications are powerful treatments, but they are prescription medicines rather than a quick fix for anyone wanting to lose a few pounds.
Eligibility depends on the medication, BMI, weight-related health conditions and where treatment is being provided. In England, for example, NICE recommends tirzepatide for adults with a BMI of 35 kg/m² or above and at least one weight-related comorbidity, with lower BMI thresholds generally used for people from some ethnic backgrounds. NHS access is being introduced in stages according to clinical need, and criteria differ for other GLP-1 medications (4).
Buying GLP-1 medications through unregulated sellers is risky because products may be counterfeit or contain incorrect or unknown ingredients. These medications should only be obtained through a legitimate prescriber and regulated pharmacy (8).
Interestingly, the food we eat also influences our own production of appetite-regulating hormones, including GLP-1. However, the normal physiological response to food is not equivalent to the much stronger and longer-lasting effect produced by these medications. Nutrition and medication therefore shouldn’t be viewed as competing approaches: good nutrition remains important alongside medication to support nutritional status, muscle, gut health and long-term health (5).
If you think GLP-1 medication might be suitable for you, talk to your GP or an appropriately qualified healthcare professional.
GLP-1-based medications aren’t suitable for everyone, and contraindications and cautions vary between individual medications. They should not be used during pregnancy or breastfeeding, and it is important to discuss existing medical conditions and other medications with your prescriber. GLP-1 and GLP-1/GIP receptor agonists should also be used with caution in people with a history of pancreatitis (8,9).
It is really important to tell your surgical and anaesthetic team if you are taking one of these medications. Because GLP-1-based medications delay stomach emptying, food may remain in the stomach despite fasting, potentially increasing the risk of aspiration during general anaesthesia or deep sedation (8).
If you take tirzepatide (Mounjaro) alongside the oral contraceptive pill, current UK advice is to use an additional barrier method or switch to a non-oral contraceptive for four weeks after starting treatment and for four weeks after each dose increase (8).
Unwanted side-effects can be unsettling at first, but gastrointestinal symptoms are often mild to moderate or short-lived, and dietary tweaks can help.
Because of their impact on digestion, many people experience nausea, vomiting, diarrhoea, constipation, indigestion or bloating, particularly when starting treatment or increasing the dose (8).
More serious side-effects are uncommon but can occur. Acute pancreatitis is a recognised adverse effect and, in January 2026, the MHRA strengthened warnings following rare reports of severe, necrotising and fatal cases. Anyone experiencing severe, persistent abdominal pain, particularly if it radiates to the back and is accompanied by nausea or vomiting, should seek urgent medical attention (9).
Semaglutide has also been associated with a very rare eye condition called non-arteritic anterior ischaemic optic neuropathy (NAION), which can cause sudden loss or rapid worsening of vision. Current UK information estimates that it may affect up to 1 in 10,000 people taking semaglutide. Anyone experiencing sudden loss or rapid deterioration of vision should seek urgent medical attention (10).
Recent international guidance highlights that GLP-1 therapy should be paired with good nutritional care, physical activity and appropriate monitoring. As appetite and food intake fall, the focus needs to be not simply on losing weight, but on protecting muscle, meeting nutritional requirements and supporting long-term health (5,11).
Here are my top tips for nutrition on GLP-1 medication:
Preserving muscles
With a poor appetite, protecting your muscles matters more than ever. Weight loss inevitably includes some loss of lean tissue alongside body fat, so adequate nutrition and resistance exercise are important.
Protein requirements should be individualised. Recent expert guidance suggests that around 1.2–1.6 g protein per kg body weight per day may be an appropriate target during active weight loss for some people, although needs will vary according to factors including body size, age, health and activity levels (5,11).
Include a good source of plant protein at each meal, for example tofu, tempeh, beans, lentils, seitan, soya chunks or mycoprotein.
Combine this with progressive resistance exercise two to three times weekly, using equipment such as weights or resistance bands, or body-weight exercises. Adequate protein alongside resistance training can help support muscle mass, strength and physical function during weight loss (5,11).
Nutrient density
With smaller portions, micronutrient density becomes critical. Choose a variety of colourful plant foods and get clued up on where you can get your vitamin B12, iron, calcium, vitamin D, iodine and omega-3 fatty acids.
Digestion and gut health
To support digestion, prevent constipation and promote gut health, include fibre-rich foods regularly. Don’t unnecessarily cut out your complex carbohydrates such as oats, brown rice, whole wheat pasta and wholemeal bread, and include vegetables, fruit, beans, lentils, nuts and seeds.
If your appetite is very low or you are experiencing significant nausea, bloating or fullness, however, huge portions of high-fibre foods may make it more difficult to meet your nutritional needs. Build fibre gradually and prioritise getting enough nutrition overall.
Hydration
Reduced food and fluid intake, alongside vomiting or diarrhoea for some people, can increase the risk of dehydration. Drink regularly throughout the day, using urine colour as a practical guide and aiming for a pale straw colour for most people.
Plant-forward eating
Putting plants at the forefront of meals and snacks can help keep nutrient density, fibre and overall dietary quality high. If you are already plant-based, aim for plenty of variety while making sure smaller meals still contain enough protein and energy.
Mindful eating
Chew well, pause between bites and eat slowly. Taking time to notice textures, flavours and fullness cues can be particularly helpful when appetite and the experience of hunger feel different while taking GLP-1 medication.
What to leave out
Rather than thinking in terms of a restrictive ‘GLP-1 diet’, focus on overall dietary quality. A pattern rich in vegetables, fruit, wholegrains, legumes, nuts and seeds provides fibre, micronutrients and other beneficial plant compounds.
A well-planned vegan or plant-forward diet can provide plenty of fibre and quality plant proteins alongside GLP-1 therapy – but when appetite is significantly reduced, meals may need to be deliberately designed to provide enough protein, energy and micronutrients.
Many unwanted side-effects can be managed with some simple nutrition and lifestyle tweaks. Here are some tips for some of the most common symptoms:
Nausea: try smaller, more frequent meals and limit very fatty or heavy meals if these make symptoms worse. Snack on dry starchy foods such as crackers and toast, take regular small sips of fluids and try cold meals if cooking smells make nausea worse.
Constipation: build fibre gradually and drink regularly throughout the day. Add kiwi and/or chia seeds with a snack or dessert and ensure daily movement. If constipation is persistent or severe, speak to your healthcare professional rather than simply continuing to increase fibre.
Reflux: eat smaller, more frequent meals, sit upright to eat and avoid lying down soon after meals. Identify your own trigger foods rather than unnecessarily restricting foods that don’t cause symptoms.
Bloating: chew food thoroughly, eat slowly, build in new high-fibre foods gradually and limit fizzy drinks if they worsen symptoms. Gentle movement after meals, such as a short walk, may also help.
Regular review is important while using GLP-1 medication, particularly if you are experiencing significant symptoms or struggling to eat enough. Tracking strength, energy, nutritional intake and bowel habits can give a more complete picture of health than weight alone (5,11).
The benefits of GLP-1-based medications can extend beyond the number on the scales. In people aged 45 or over with overweight or obesity and established cardiovascular disease, but without diabetes, the SELECT trial found that semaglutide reduced the relative risk of major cardiovascular events by 20% compared with placebo (12).
Research is continuing into the effects of GLP-1-based therapies across a growing number of health conditions, but it is important not to assume benefits for conditions where robust clinical evidence and regulatory approval have not yet been established.
GLP-1-based medications can profoundly change appetite and the quantity of food someone wants to eat. That makes the quality of the food that remains even more important.
Without attention to nutrition during significant weight loss, there is a risk of inadequate protein and micronutrient intake and loss of lean tissue. These medications can be a powerful evidence-based treatment for obesity, but medication and nutrition are not competing approaches. Good nutritional care can help people get the most from treatment while protecting muscle, nutritional status and long-term health.
It is also important to recognise that obesity is a chronic condition. For many people, stopping medication leads to increased appetite and substantial weight regain. This is a biological response rather than a failure of willpower, and ongoing treatment and/or long-term behavioural and nutritional support may be needed (6,7).
If you’re using or considering a GLP-1 medications, here are the habits that make all the difference:
If you’d like to learn how to lose weight confidently on a plant-based diet, with or without medication, join my free masterclass: Why You’re Still Struggling to Lose Weight on a Plant-Based Diet.
In just 1 hour, you’ll discover how to manage cravings and build habits that support your health for the long term.
Whether you use medication or not, nutrition remains an important part of looking after your health. And remember, GLP-1 therapy should be stigma-free, person-centred and equitable… these medications are a tool, not a shortcut or a moral choice.
Written by Rosemary Martin RD October 2025, updated September 2026
If you’re looking for more, why not join our very popular FREE Masterclass – Why You’re Still Struggling to Lose Weight on a Plant-Based Diet. Just choose the next date and time that suits you and we will see you there!
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