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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Forcing Yourself to Eat on Mounjaro — What You Need to Know
When you start Mounjaro (tirzepatide), one of the most common experiences is a dramatic reduction in appetite. Many people find themselves needing to actively remind themselves to eat, or simply not feeling hungry at mealtimes. This is an expected effect of how Mounjaro works, but it can feel uncomfortable or challenging. Understanding why this happens, how it compares to other weight loss medications like Wegovy, and when to contact your GP is important for managing your treatment safely.
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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 Appetite — and How It Compares to Wegovy
Mounjaro is a dual GIP and GLP-1 receptor agonist, meaning it activates two different hormone pathways that regulate hunger and fullness. This dual mechanism is more potent than medications that target only one pathway. The tirzepatide in Mounjaro signals your brain that you're full more quickly and reduces cravings significantly — which is why appetite suppression is so pronounced, especially in the first 4–8 weeks.
Wegovy (semaglutide), by contrast, is a GLP-1 agonist only — it activates just one hormone pathway. Clinical trial data shows:
- Mounjaro users (SURMOUNT trials): reported reduced appetite as a dominant effect, with average weight loss of ~15–21% body weight
- Wegovy users (STEP trials): also report appetite reduction, but typically less intense than Mounjaro, with average weight loss of ~15% body weight
Both medications slow gastric emptying (how quickly food leaves your stomach), but Mounjaro's dual action tends to create a more pronounced "not hungry" sensation. This explains why some people on Mounjaro report finding it harder to eat adequate calories, whilst others on Wegovy experience more moderate appetite changes.
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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.
When Appetite Loss Is Normal — and When to Contact Your GP
Some appetite reduction is expected and desired on Mounjaro — that's how it helps create a calorie deficit for weight loss. However, you should still aim to eat enough to maintain your health. During dose titration (weeks 1–20+ as your dose increases from 2.5 mg to your maintenance dose), appetite changes can be most noticeable. This typically settles slightly as your body adjusts.
Contact your GP or prescriber if: you're unable to eat enough to meet basic nutritional needs, you experience severe nausea or vomiting that prevents eating, you have signs of malnutrition or rapid muscle loss, or you're struggling mentally with the appetite suppression. Your prescriber can assess whether dose adjustment, timing of meals, or additional support is needed. You can also use our free GLP-1 weight loss calculator to track whether your weight loss is progressing at a healthy, sustainable rate — rapid loss may indicate undereating.
- 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 it dangerous to force myself to eat when not hungry on Mounjaro?
No — it's important to eat regular, balanced meals even if you don't feel hungry, to maintain muscle mass, energy, and nutritional intake. "Forcing" doesn't mean forcing down large quantities; it means eating regular, nutrient-dense portions on a schedule. If you're genuinely unable to eat, contact your GP.
Does Wegovy cause less appetite loss than Mounjaro?
Clinical evidence suggests Wegovy's appetite suppression is typically less intense than Mounjaro's, due to semaglutide being a GLP-1 agonist only rather than dual GIP+GLP-1. However, individual responses vary significantly — some Wegovy users report very strong appetite loss too.
How long does intense appetite loss last on Mounjaro?
Appetite changes are usually most noticeable during dose titration (the first 20 weeks as you progress through doses). Many people report appetite settling slightly after reaching their maintenance dose, though reduced appetite remains part of how the medication works.
What should I eat if I'm not hungry on Mounjaro?
Focus on nutrient-dense foods: protein (chicken, fish, eggs, Greek yoghurt), healthy fats (avocado, olive oil, nuts), and vegetables. Eat smaller, regular meals rather than large ones. Liquid nutrition like smoothies can help if solid food feels unappealing.
Should I stop taking Mounjaro if I can't eat normally?
No — discuss your concerns with your prescriber first. They can assess your specific situation, check your nutritional intake, and decide if dose adjustment or strategies to support eating might help. Never stop medication without medical guidance.
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.