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

01 · The core answer

What is the GLP-1 diet?

It is a way of eating built around the way these medicines change appetite. Tirzepatide activates two natural gut-hormone receptors, GIP and GLP-1, which help regulate appetite and slow how quickly the stomach empties.¹ Most people feel fuller sooner and less hungry between meals, which supports a reduced-calorie diet.¹

So the diet is less about willpower and more about making smaller appetites count. If you can only manage modest meals, each should carry protein, fibre and nutrients. For a closer look at the plate itself, see our guide to a balanced approach on treatment.

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

02 · Your decision

Is this relevant to me, and what next?

It is relevant if you are taking a GLP-1 or GIP/GLP-1 medicine, or considering one. If you are weighing up treatment, our weight loss clinic explains how a free online consultation works, and the Mounjaro pen starts at £169.99 for the 2.5mg strength (standard price, checked 10 October 2026).

If you are already treated, focus on habits rather than a named diet. A set of practical recommendations gives more detail on everyday habits.

Related guides: What's glp 1 diet and What does a glp 1 diet consist of and Glp 1 weight loss diet.

03 · What to eat and limit

What to eat and what to limit

No food is banned on Mounjaro, including bananas, but some choices make treatment easier and more effective.¹ Prioritise protein at each meal, vegetables and fibre, and regular fluids.

Many people feel worse after very fatty, fried or very sugary food. Large portions sit heavily because the stomach empties more slowly, so smaller, slower meals work better.¹³

Sensible protein sources include fish, eggs, poultry, pulses, tofu and dairy. Fibre comes from oats, beans, lentils and vegetables. Your prescriber or a dietitian can tailor protein and fibre amounts to you.

04 · Protect your muscle

Protein, muscle and exercise

Protein matters because some of any rapid weight loss comes from lean tissue, and protecting muscle protects your metabolism, strength and appearance.

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

Increased physical activity is part of the licence, not an optional extra. Regular moderate activity such as brisk walking, plus resistance work, is the evidence-backed pattern. Start where you are and build. On injection days with early side effects, lighter movement still counts, and exercise also protects against regain if you later stop treatment.

05 · Fluids, coffee and alcohol

Fluids, coffee and alcohol

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. Keep water within reach through the day. Inability to keep fluids down is a reason to contact your clinical team, not something to push through.

Coffee and tea are fine, as there is no interaction between Mounjaro and caffeine. 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. Coffee rules circulating on social media have no clinical basis.

There is no direct interaction between Mounjaro and alcohol, 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.

06 · Supplements and myths

Vitamins, supplements and natural GLP-1 claims

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.

Supplements sold as natural GLP-1 boosters are not equivalents and are not substitutes for prescribed treatment. Oral supplements, like other oral products, may be absorbed more slowly when you start treatment. Foods rich in fibre and protein support fullness, but they do not replicate a prescribed medicine.

07 · Does it work?

What the evidence says about 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

Mounjaro is available on the NHS, but access is being phased in over several years, and many people who meet the licensed criteria choose regulated private treatment. Mounjaro is a prescription-only medicine, supplied only after an online consultation reviewed by a GPhC-registered prescriber.