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
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Diet Plan On Mounjaro vs Wegovy — What You Need to Know
If you're considering Mounjaro or Wegovy for weight management, understanding how to structure your diet around either medication is crucial. Both GLP-1 and dual GIP/GLP-1 medications work alongside dietary changes, not instead of them. The key difference lies in their mechanisms: Mounjaro (tirzepatide) activates two hormone pathways, whilst Wegovy (semaglutide) targets one. This affects appetite suppression, meal frequency, and how your body responds to food. Your diet strategy will depend on which medication suits you best—a decision made during clinical assessment with your prescriber. This guide compares diet approaches for both options so you can understand what to expect.
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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 Affect Your Diet Differently
Mounjaro (tirzepatide) works via dual GIP and GLP-1 receptor activation, creating a stronger appetite suppression signal. In clinical trials (SURMOUNT-1), participants on Mounjaro 15 mg lost approximately 20.9% of body weight over 72 weeks when combined with reduced-calorie diet and physical activity. This dual mechanism often means smaller portion sizes, reduced cravings, and less frequent eating—some people naturally shift to two meals daily rather than three.
- Slower stomach emptying (gastric effect typically decreases over weeks)
- Strong satiety signals—feeling fuller with less food
- Reduced interest in high-fat, high-sugar foods
- May need fewer structured meals; body signals fullness clearly
Wegovy (semaglutide) is a single GLP-1 agonist. Clinical trial data (STEP-1) showed average weight loss of approximately 14.9% body weight at 68 weeks on the 2.4 mg maximum dose alongside lifestyle changes. The appetite suppression is effective but via one pathway rather than two. Diet structure often remains similar to Mounjaro but with naturally smaller portions and reduced snacking.
- GLP-1 mechanism reduces hunger and increases fullness perception
- Weight loss achieved through portion control and reduced frequency
- Fewer cravings, particularly for sugary foods
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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.
Building Your Diet Plan: Practical Guidance for Both Medications
Regardless of whether your prescriber recommends Mounjaro or Wegovy, your diet plan should follow NHS guidelines: a sustainable calorie deficit alongside increased physical activity. Most people find that the medication naturally supports this by reducing hunger—you don't need special "Mounjaro meals" or restrictive eating. Instead, focus on nutrient-dense foods: lean proteins, vegetables, whole grains, and healthy fats. Avoid very low-calorie diets (under 800 kcal/day) unless under medical supervision. Track your intake using food logging or our free progress tracker to monitor both weight and how you feel. Some people experience nausea or altered appetite early on—eating smaller, more frequent meals helps until your body adjusts (usually 2–4 weeks). Hydration is essential. Your GP or prescriber can refer you to a dietitian for personalised guidance.
- 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.
Do I need a special diet plan when starting Mounjaro or Wegovy?
No—both medications work best alongside standard healthy eating principles: calorie deficit, balanced nutrition, and increased activity. The medication supports your efforts by reducing appetite. NHS dietitian guidance applies equally. Some people prefer smaller, more frequent meals initially if experiencing nausea; this settles after 2–4 weeks as your body adjusts.
Which medication requires stricter dieting—Mounjaro or Wegovy?
Neither requires stricter dieting. Both work alongside the same NHS-recommended approach: sustainable calorie deficit and balanced meals. Mounjaro's dual mechanism may create stronger satiety signals, meaning some people naturally eat less without conscious restriction. Individual response varies—your prescriber will monitor progress and adjust your dose if needed.
Can I follow low-carb or intermittent fasting on Mounjaro or Wegovy?
Yes, though it's not necessary. Both medications work with any eating pattern. Low-carb diets and intermittent fasting can accelerate weight loss but may increase fatigue or nausea when combined with appetite-suppressing medication. Discuss any structured diet plan with your GP or prescriber before starting, especially if taking diabetes medication alongside these injections.
How quickly will I see weight loss results on diet plus medication?
Clinical trials show meaningful weight loss within 4–12 weeks of consistent use alongside dietary changes. However, individual timelines vary—some people lose weight steadily; others experience a plateau before a sudden drop. Use our GLP-1 weight loss calculator to see projected outcomes at different doses. Track progress with our free progress tracker, focusing on how you feel, not just the scales.
What if I feel unwell or struggle with nausea whilst on my diet plan?
Nausea is common in the first 2–4 weeks and typically improves. Eat smaller, frequent meals rather than large ones; stay hydrated; avoid greasy or very spicy foods. If nausea persists beyond 4 weeks or worsens, contact your prescriber—dose adjustment may help. Never skip meals or under-eat to manage side effects; always discuss symptoms with your healthcare provider.
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.