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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How Much Should You Eat On Mounjaro Compared To Wegovy?
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are prescription-only weight management injections that change how much you feel like eating — but they work slightly differently. Mounjaro is a dual GIP and GLP-1 receptor agonist, while Wegovy uses GLP-1 only. This means the appetite suppression and portion control effects can vary between the two medications. There's no "correct" amount to eat; instead, both work by helping you naturally feel fuller on smaller portions. Your prescriber will guide you on managing your intake as your body adjusts to treatment.
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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 Appetite — Key Differences
Mounjaro's dual mechanism: Because Mounjaro activates both GIP and GLP-1 pathways, it may produce stronger appetite suppression than GLP-1-only medications. Clinical trial data from SURMOUNT-1 showed participants lost an average of 20.9% of body weight at the maximum 15 mg dose over 72 weeks — often reporting significantly reduced hunger and earlier fullness during meals.
Wegovy's GLP-1 mechanism: Wegovy activates the GLP-1 pathway alone, producing reliable appetite reduction. STEP-1 trial data showed average weight loss of approximately 14.9% at the maximum 2.4 mg dose. Users typically report feeling satisfied with smaller meals and fewer cravings, though the appetite suppression may be somewhat less intense than Mounjaro's dual action.
Individual variation: Some people find Mounjaro's appetite suppression very strong (especially at higher doses), whilst others experience comparable effects from Wegovy. Your response depends on your metabolism, how your body's GIP and GLP-1 receptors respond, and individual factors. A prescriber will assess which suits you better based on your medical history and response to any previous treatment.
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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.
Practical Guidance — What To Eat During Treatment
Neither Mounjaro nor Wegovy comes with a strict diet plan — appetite reduction happens naturally as the medication takes effect. However, healthcare guidance suggests focusing on nutrient-dense foods: lean protein, vegetables, wholegrains, and healthy fats. Eating slowly and chewing thoroughly helps you notice fullness signals earlier. Many users find they need to eat less simply because hunger diminishes; forcing yourself to eat when not hungry is unnecessary and uncomfortable.
Some people on these medications experience mild nausea or reduced appetite for certain foods (often fatty or heavily processed options), which naturally supports healthier choices. If you find yourself eating very little (under 800 kcal/day consistently), discuss this with your GP or prescriber — they may adjust your dose or provide nutritional guidance. Use our GLP-1 weight loss calculator to see projected outcomes, and track your progress with our free progress tracker as your appetite and eating patterns settle.
- 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.
Will I need to follow a strict diet on Mounjaro or Wegovy?
No. Both medications reduce hunger naturally, so a calorie deficit occurs without strict dieting. Focus on balanced, nutrient-dense foods rather than calorie counting. Your prescriber may suggest basic healthy eating principles, but the medication does much of the appetite regulation for you.
Is Mounjaro stronger than Wegovy for appetite suppression?
Clinical trial data suggests Mounjaro may produce slightly stronger appetite reduction due to its dual GIP and GLP-1 mechanism, but individual responses vary significantly. Some people respond equally well to Wegovy. Your prescriber will assess which is more suitable based on your personal circumstances and medical history.
What if I'm eating too little on Mounjaro?
If you're consistently eating under 800 kcal/day or feel unwell, contact your GP or prescriber. They may reduce your dose, check for side effects like nausea, or provide nutritional advice. Severe undereating isn't the goal — sustainable, adequate nutrition is important for health.
Can I still eat foods I enjoy on these medications?
Yes, but portion sizes typically decrease naturally. Many users find they can eat their favourite foods but feel satisfied with less. Some experience changes in food preferences (fatty foods may feel unappealing). Both medications work alongside normal eating rather than replacing it with special foods.
Which medication is better for me — Mounjaro or Wegovy?
This is a personalised decision based on your BMI, weight-related health conditions, medical history, and individual factors. Both require a prescription and clinical assessment from a UK prescriber. Your GP or specialist will recommend the most suitable option after evaluating your specific situation.
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.