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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Loss of Appetite and Losing Weight — What You Need to Know
Loss of appetite can be a natural part of weight loss, but it's important to understand what's happening and whether it's safe. Appetite changes can occur for many reasons — from dietary adjustments to medical conditions — and managing them properly is key to sustainable weight loss. This guide explains how reduced appetite relates to weight loss, when it's helpful, and when you should speak to your GP about significant appetite changes.
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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 Appetite and Weight Loss Connect
Appetite is controlled by hormones and signals from your brain and gut. When you reduce calorie intake or increase physical activity, your body naturally adjusts these signals, which can lead to reduced hunger.
Healthy appetite changes during weight loss include:
- Feeling fuller after smaller meals
- Reduced cravings for high-calorie foods
- Naturally eating less without feeling deprived
- More stable energy levels
However, appetite loss can also signal that you're not eating enough nutrients. The NHS recommends sustainable weight loss of 0.5 to 1 kg per week — slower loss is safer and helps preserve muscle mass. If you've lost your appetite significantly, it's worth checking your diet includes adequate protein, healthy fats, and micronutrients. Use our free BMI calculator to establish your healthy weight range, then work backwards to a sustainable calorie deficit rather than restricting too aggressively.
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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.
Prescription Medications and Appetite Loss
Some prescription weight loss medications, including GLP-1 receptor agonist injections, work partly by reducing appetite. Medications like Wegovy (semaglutide) and Mounjaro (tirzepatide) are licensed in the UK for weight management and may help people feel fuller after smaller meals.
These medications require a prescription and clinical assessment — they're not suitable for everyone. Common side effects include nausea and reduced appetite, especially in the first few weeks. Our GLP-1 weight loss calculator can help you understand projected outcomes at different doses if you're considering prescription weight loss support. Always discuss any appetite changes with your prescriber, as they may adjust your dose or provide guidance on managing side effects safely.
- 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 loss of appetite during weight loss normal?
Yes, mild appetite reduction is common when you eat fewer calories or change your diet. However, it should not be extreme. If you've lost interest in all foods, feel nauseous, or haven't eaten for days, contact your GP. These may signal nutritional deficiency or another health issue requiring investigation.
How can I maintain nutrition if I've lost my appetite?
Focus on nutrient-dense foods even if portions are smaller — eggs, fish, leafy greens, nuts, and yoghurt provide protein and micronutrients efficiently. Eat smaller, more frequent meals rather than three large ones. Consider a multivitamin if recommended by your GP. Use our progress tracker to monitor weight loss — rapid loss combined with appetite loss may mean you're undereating.
Can GLP-1 medications like Wegovy cause appetite loss?
Yes. Wegovy and similar GLP-1 injections work partly by reducing appetite. This is often a beneficial effect for weight management, but nausea and reduced appetite are common side effects, especially when starting or increasing doses. These usually improve over time. Always report significant appetite loss to your prescriber.
When should I see my GP about appetite changes?
Contact your GP if: appetite loss lasts more than two weeks, you're losing weight unintentionally, you feel weak or dizzy, you can't eat solid foods, or appetite loss is accompanied by other symptoms like pain or mood changes. Appetite changes can signal underlying conditions including infections, hormonal imbalances, or medication side effects.
What's the safest way to lose weight without extreme appetite loss?
The NHS recommends a calorie deficit of approximately 500 kcal per day for sustainable loss of 0.5–1 kg per week. This approach typically causes mild, manageable appetite reduction rather than extreme hunger loss. Include adequate protein (helps you feel fuller), stay hydrated, and focus on whole foods. Weight loss support through NHS weight management programmes or your GP can provide personalised guidance for safe, sustainable results.
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.