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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What Diet Changes Should You Make on Mounjaro?
Mounjaro (tirzepatide) is a prescription-only injection that works by reducing appetite and helping you feel fuller after smaller meals. But taking Mounjaro isn't a substitute for healthy eating—it's designed to work alongside dietary changes. Many people find their relationship with food naturally shifts on Mounjaro, but understanding how to eat well during treatment helps you get the best results. This guide explains what to expect and how to approach nutrition while taking this medication.
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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 Affects Your Appetite and Eating
Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two natural hormone pathways that regulate hunger and fullness. When you start Mounjaro or increase your dose, you'll typically notice reduced appetite, less interest in certain foods (especially fatty or sugary items), and feeling satisfied after eating smaller portions. Some people experience reduced food cravings and less frequent hunger signals throughout the day.
In the SURMOUNT-1 clinical trial, participants taking Mounjaro achieved average weight loss of 15–21% of body weight when combining the medication with a reduced-calorie diet and increased physical activity. However, individual results vary significantly.
Early doses (2.5 mg to 5 mg) may produce mild appetite suppression, while higher doses (10–15 mg) typically create more noticeable changes in how much food you want to eat. It's important to listen to your body and eat when you're genuinely hungry, rather than forcing meals.
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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
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Practical Eating Strategies While On Mounjaro
Focus on nutrient-dense, lower-calorie foods: lean proteins (chicken, fish, eggs, yoghurt), vegetables, whole grains, and healthy fats. Eat slowly and chew thoroughly—Mounjaro slows stomach emptying, so rushing food can increase nausea. Stay hydrated with water throughout the day.
Many people find small, frequent meals easier to manage than three large meals. If nausea is troublesome, stick to bland foods temporarily: plain chicken, rice, toast, or soup. Avoid fatty, fried, or heavily spiced foods, which can worsen side effects. Keep a food diary or use our free progress tracker to monitor what you eat and how you feel—this helps identify patterns and foods that work well for you.
Remember: Mounjaro is most effective when combined with reduced-calorie intake and regular physical activity. Your prescriber or a registered dietitian can provide personalised nutrition 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.
Will Mounjaro stop me from eating normally?
Mounjaro reduces appetite and hunger signals, so you'll likely eat less and feel fuller sooner. You'll still be able to eat normal foods, but portion sizes often decrease naturally. Most people find they can eat a balanced, varied diet—just smaller amounts. If appetite loss becomes extreme or concerning, speak to your prescriber.
What if I feel nauseous on Mounjaro—what should I eat?
Nausea is common, especially during dose increases. Try bland, easy-to-digest foods: plain chicken, rice, toast, crackers, broth, or ginger tea. Avoid fatty, spicy, or rich foods. Eat slowly and in small amounts. Drink water regularly but sip rather than gulp. Nausea typically improves within a few days of each dose increase.
Should I count calories while on Mounjaro?
Calorie awareness is helpful—Mounjaro works best alongside a reduced-calorie diet (typically 500 kcal deficit for sustainable loss). However, you don't need to obsessively count. Focus on eating protein, vegetables, and whole grains; avoiding ultra-processed foods; and stopping when full. Your GP or a dietitian can advise on appropriate calorie targets for you.
Can I drink alcohol while taking Mounjaro?
Yes, but in moderation. Alcohol is high in calories and may increase nausea or stomach irritation, especially on higher doses. It can also lower blood sugar if you take other diabetes medications. Limit alcohol and always eat food with it. Discuss safe limits with your prescriber if you have questions.
How long does it take for appetite to change on Mounjaro?
Many people notice reduced appetite within 3–5 days of their first injection or dose increase. The effect typically plateaus by around day 7–10 of each dose. Some people adjust within 4 weeks (one cycle); others take longer. Changes in appetite are individual and may evolve as your body adapts to the medication.
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.