GLP-1 and Nutrition: What to Eat on Treatment (October 2026)

01 · The core answer

What good nutrition looks like on a GLP-1 medicine

The most useful rule is to make every meal count, because you will be eating less. Tirzepatide activates the GIP and GLP-1 receptors, which helps regulate appetite and slows how quickly the stomach empties.¹ Most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.

That is helpful for weight loss, but it also means a small appetite can be spent on the wrong things. A few biscuits and a latte can fill you up while delivering little protein, fibre or micronutrients. The aim is a sustainable calorie deficit, not a perfect food list.¹

In practice, four habits cover most of what matters:

• Protein at every meal. Start the meal with it, before the sides.
• Vegetables and fibre. They support digestion and keep portions satisfying.
• Regular fluids. Reduced appetite means less water arrives with your food.
• Smaller, slower meals. Large portions sit heavily because the stomach empties more slowly.

If you want a deeper practical walkthrough, our GLP-1 nutrition support guide goes through meal structure in more detail.

02 · Your next step

Do you need a special diet plan?

Most people do not need a special diet, but they do benefit from a little structure. Treatment is licensed alongside a reduced-calorie diet and increased physical activity, so nutrition is part of the treatment rather than an extra.¹ Think of it as protecting what you want to keep (muscle, energy, regular digestion) while the medicine reduces what you want to lose.

You do not need a branded shake, a powder or a 'GLP-1 friendly' range. Ordinary food prepared simply does the job for most people, and a pharmacist or dietitian can help if you have a medical condition, food intolerance or a very small appetite.

If you are still deciding whether treatment is right for you, our weight loss clinic explains the options. If you are ready, your consultation is reviewed by a GPhC-registered prescriber. Ongoing monthly reviews are included, so nutrition questions can be raised as you go.

Related guide: Agonisti glp 1.

03 · Protein and muscle

Protein and muscle: why it matters most

Protein is the single nutrient to get right, because some of any rapid weight loss comes from lean tissue. Protecting muscle protects your metabolism, strength and appearance.¹

There are two levers. The first is adequate protein: include a protein source at every meal, which is harder when appetite is low. The second is resistance exercise two or more times a week. This matters more, not less, as the dose rises and appetite falls.¹

You will see precise gram targets quoted online. Your prescriber, pharmacist or a registered dietitian can set a personal target.

Practical ways to get protein in when you are not hungry:

• Eat the protein portion first, then add vegetables or carbohydrate if you still have room.
• Choose easy options: eggs, fish, poultry, lean meat, tofu, beans, lentils, cottage cheese and Greek-style yoghurt.
• Split intake into small, regular meals rather than forcing a large plate.
• Keep ready-to-eat items nearby, such as boiled eggs or plain yoghurt, for days when cooking feels like too much.

For a plant-based diet, combine pulses, soya, grains and nuts through the day. Smaller portions of these are filling, so spread them out.

04 · Fibre and digestion

Fibre, vegetables and digestion

Vegetables and fibre are on the short list of priorities because they help keep digestion moving while the stomach empties more slowly.¹ Constipation is a common complaint when eating and drinking less, so fibre and fluid work as a pair.

Build up gradually. A sudden jump in raw vegetables, bran or pulses on top of slower emptying can leave you bloated and uncomfortable. Cooked, softer vegetables, oats, fruit, wholegrain bread and pulses are easier starting points than large raw salads.

Pair added fibre with extra water. Fibre without fluid can make constipation worse, not better. If constipation or other digestive symptoms persist, speak to a pharmacist or your prescriber before reaching for a remedy.

Our Mounjaro nutrition explainer looks at how common food groups sit with the medicine in more depth.

05 · Foods to limit

What foods should you not eat on a GLP-1?

No food is banned on Mounjaro, including bananas, but some choices make treatment easier and more effective.¹ Many people feel worse after very fatty, fried or very sugary food, and large portions sit heavily because the stomach empties more slowly.¹

So rather than a forbidden list, think about what tends to cause trouble:

• Greasy, fried or heavily creamy dishes. Many people feel worse after very fatty or fried food.
• Very sugary food and drinks. They add calories without protein or fibre and are easy to overeat in liquid form.
• Big portions. A plate that looked normal before treatment may now be too much. Stop at comfortable, not full.
• Eating quickly. Slow meals give your fullness signals time to catch up.

Social media 'rules' about particular foods and drinks often have no clinical basis. If something upsets you, note it, cut back and try again later. If symptoms are severe or persistent, tell your prescriber.

06 · Hydration

Hydration on a GLP-1 medicine

Drinking enough matters more on Mounjaro than usual. Reduced appetite means less fluid from food, and vomiting or diarrhoea can dehydrate you quickly, which is the main route to the rare kidney problems reported with this class.¹

Keep water within reach through the day. Sipping steadily is usually easier than drinking large amounts at once, particularly when your stomach feels full. Tea, coffee, soup and diluted squash all contribute.

Treat inability to keep fluids down as a contact-your-clinical-team issue, not something to push through.¹ Signs that you may be running dry include dark urine, dizziness, a dry mouth and unusual tiredness. Do not wait for them to get worse.

07 · Coffee and alcohol

Coffee, tea and alcohol

Coffee and tea are fine, because there is no interaction between Mounjaro and caffeine.¹ Two practical notes apply. Strong coffee on an empty, slower-emptying stomach can aggravate nausea or reflux for some people, and high-calorie coffee drinks are an easy place for the calorie deficit to leak.

That second point is one answer to a question many people ask: why am I gaining weight, or not losing, on a GLP-1? Liquid calories from sweetened lattes, juices, smoothies and alcohol slip past the fullness signals. They are worth checking before assuming the medicine has stopped working.

Alcohol has no direct interaction with Mounjaro, but drinking on a reduced appetite and emptier stomach can hit harder than usual, and alcohol adds calories that work against your goals. If you also take insulin or a sulfonylurea, alcohol increases the risk of low blood sugar. Moderation is the sensible rule, and many people find their desire for alcohol drops on treatment.¹

08 · Supplements and shakes

Supplements, shakes and 'GLP-1 nutrition' products

No supplement is required with Mounjaro, but eating much less can leave gaps, so a standard daily multivitamin is a reasonable safety net while losing weight. Discuss anything beyond that with a pharmacist.¹

A protein shake is simply a convenient protein source, useful on days when solid food is unappealing, and it is no more 'GLP-1 compatible' than any other. Check the label for what it contains and what it adds in calories.

Supplements sold as 'natural GLP-1 boosters' are not equivalents and are not substitutes for prescribed treatment.¹ Marketing that makes dramatic weight-loss claims should be read sceptically. These products are low-cost supplements with no clinical oversight and dosing is not standardised.

One further point: oral supplements, like other oral products, may be absorbed more slowly when you start treatment.¹ If you take a medicine that needs to work on a tight schedule, ask a pharmacist how to time it. For the biology behind the hype, see our explainer on AMPK and GLP-1.

09 · Exercise

Exercise: the other half of the plan

Increased physical activity is part of the licence, not an optional extra.¹ Nothing special is required: the evidence-backed pattern is regular moderate activity, such as brisk walking, plus resistance work for muscle.

Start where you are and build. On injection days with early side effects, lighter movement still counts. Resistance work can be weights, bands, bodyweight or classes, and it is the one that most directly supports the protein you are eating.

Exercise also protects against regain if you later stop treatment.¹ Building the habit during treatment is one of the more useful things you can do for the long term.

10 · Evidence on results

What the trials say about diet and results

In the SURMOUNT-1 trial of 2,539 adults, people taking tirzepatide alongside diet and exercise lost on average 15% of their body weight on 5mg, 19.5% on 10mg and 20.9% on 15mg over 72 weeks, compared with 3.1% with lifestyle changes alone.²

These are trial averages. Individual results vary, and treatment works alongside a reduced-calorie diet and increased physical activity, not instead of them.² For someone starting at 100 kg, 20.9% is about 21 kg, but your own result depends on dose, adherence, how you eat and how your body responds.

The takeaway for nutrition is that the medicine and the food choices work together. Medicine lowers appetite; nutrition decides what that smaller appetite is spent on.

11 · Side-effect days

Eating on rough days and when to get help

On days when nausea or reflux are present, simple and small is the best approach. Bland, low-fat foods, cold options, fluids in small sips and an earlier, lighter evening meal tend to be better tolerated than rich or large meals.

Do not force down large amounts of food to hit a target. Prioritise fluids and a small protein source, then return to your normal pattern when you feel better. If symptoms persist, speak to your prescriber, who can advise on the dose and timing.

Get medical help straight away if you cannot keep fluids down, and read the patient information leaflet for the full list of side effects and when to seek urgent help.¹³ You can report suspected side effects through the Yellow Card scheme.¹⁹

Our GLP-1 nutrition deep dive covers the food science.

12 · A sample day

A simple day of eating on a GLP-1

A workable day puts protein first, adds vegetables and fibre, and keeps portions modest. Treat the following as an illustration, not a prescription.

Treatment is licensed alongside a reduced-calorie diet, so the aim is a sustainable deficit, not a perfect food list.¹

13 · Serious side effects

Serious side effects: when to get help straight away

Serious side effects are uncommon but need urgent attention. Seek immediate medical help for: severe, persistent stomach pain that may spread to your back, with or without vomiting (possible pancreatitis); pain in the upper right abdomen, fever or yellowing of skin/eyes (possible gallbladder problems); or signs of a severe allergic reaction such as swelling of the face or throat and difficulty breathing. If you take insulin or a sulfonylurea alongside Mounjaro, watch for low blood sugar (shakiness, sweating, confusion) — your prescriber may need to adjust those medicines.¹

14 · Access and the NHS

NHS dietary support and private treatment

Mounjaro is available on the NHS, but access is being phased in over several years.⁶ NICE sets the eligibility criteria, and your GP or local service can tell you where you stand.⁴ Many people who meet the licensed criteria choose regulated private treatment rather than waiting.

Whichever route you take, ask what nutrition and activity support is included. With us, your consultation is free and reviewed by a GPhC-registered prescriber, and ongoing monthly reviews and side-effect support are part of the service. Mounjaro is supplied directly through official LillyDirect supply, with free next-day tracked delivery in temperature-controlled packaging.