The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
Best Diet On Mounjaro: What Works With This Medication?
The best diet on Mounjaro combines a reduced-calorie approach with balanced nutrition and regular physical activity — the medication works alongside lifestyle changes, not instead of them. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist that helps regulate appetite and support feeling fuller after meals. The medication's effectiveness depends on your individual commitment to dietary changes. Many UK adults wonder how Mounjaro compares to Wegovy, another popular GLP-1 injection. Both require prescription and clinical assessment through a UK-licensed prescriber. Understanding how each medication works with diet can help you and your GP make an informed decision about which is right for your situation.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
How Mounjaro And Wegovy Work Differently With Diet
Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist — meaning it activates two hormone pathways rather than one. In the SURMOUNT-1 clinical trial, participants taking Mounjaro alongside a reduced-calorie diet and increased physical activity lost an average of 15–21% of their body weight over 72 weeks, depending on dose. The dual mechanism may help more effectively regulate appetite and reduce cravings.
Wegovy (semaglutide) is a GLP-1-only receptor agonist. In the STEP-1 clinical trial, participants lost approximately 14.9% of their body weight at the highest dose over 68 weeks. Wegovy works through a single hormone pathway, which is still highly effective but may differ slightly in how it supports appetite reduction compared to Mounjaro.
- Mounjaro: dual GIP+GLP-1 mechanism, up to 15 mg weekly dose
- Wegovy: GLP-1 only, up to 2.4 mg weekly dose
- Both: require reduced-calorie diet and physical activity for best results
- Clinical trial data shows both are effective — individual results vary significantly
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
What Diet To Follow: General Principles For Both Medications
Whether you choose Mounjaro or Wegovy, your diet should focus on whole foods, adequate protein, and consistent calorie reduction. The NHS recommends a deficit of around 500 kcal per day for sustainable weight loss of 0.5–1 kg per week. Because both medications slow gastric emptying and help you feel fuller, many people naturally eat smaller portions and choose nutrient-dense foods.
Key dietary principles: eat plenty of vegetables and lean protein; stay hydrated; avoid foods that trigger nausea (especially early in treatment); eat slowly; take oral medications separately from food if prescribed; log your intake using a food tracking app or our free progress tracker to monitor patterns. Your prescriber or a registered dietitian can provide personalised dietary guidance based on your medical history and goals.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
Is one medication better than the other for diet?
Both Mounjaro and Wegovy work effectively with dietary changes. Mounjaro showed slightly higher average weight loss (15–21%) compared to Wegovy (14.9%) in clinical trials, but individual results vary significantly. Your prescriber will assess which is more suitable based on your health, eligibility, and personal circumstances — not on diet alone.
Can I eat normally while taking Mounjaro or Wegovy?
You can eat normal foods, but portion sizes typically reduce naturally because the medication helps you feel fuller. A reduced-calorie diet is still required for weight loss. Most people find they need to eat smaller, more frequent meals early in treatment. Nausea is common initially — eating bland, protein-rich foods and staying hydrated helps. Your appetite may normalise as your body adjusts to the medication.
What if I struggle to stick to a diet on these medications?
Discuss this with your GP or the prescriber who manages your medication. A registered dietitian can provide personalised advice. Some people find the medication makes dietary adherence easier because appetite naturally reduces. Our free progress tracker can help you log meals and identify patterns. If you're not losing weight, your prescriber may adjust your dose or explore other factors affecting results.
How long does it take to see weight loss results?
Most people begin noticing changes within 2–4 weeks, though significant weight loss typically becomes evident after 8–12 weeks of consistent use alongside a reduced-calorie diet. The SURMOUNT and STEP trials measured results over 68–72 weeks. Results depend on dose, adherence, diet quality, and physical activity. Your GP can monitor progress using our free BMI calculator or weight converter to track changes in your measurements.
Do I need to follow a specific diet type like low-carb or keto?
No specific diet type is required — calorie deficit matters most. Some people find low-carb approaches reduce nausea, while others prefer balanced macronutrients. The Mediterranean diet is well-evidenced for long-term health. What matters is choosing an approach you can sustain alongside the medication. Work with your prescriber or a dietitian to create a plan that fits your lifestyle and health goals.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.