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 Weight Loss Medications Decrease Appetite
Feeling less hungry is one of the main ways prescription weight loss medications help people manage their weight in the UK. Weight loss injections like Wegovy and Mounjaro work by activating natural appetite-control hormones in your body, which signals to your brain that you're satisfied after eating smaller amounts. This decreased appetite doesn't feel forced or unpleasant — it's a gentle biological shift that can make sustainable weight management feel easier. Understanding how this works can help you decide whether prescription weight loss treatment might be right for you.
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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 GLP-1 Medications Reduce Appetite
Weight loss injections used for NHS weight loss and prescription weight loss in the UK contain GLP-1 receptor agonists — these are medications that mimic a natural hormone your gut produces after eating. Wegovy (semaglutide) is the UK-licensed GLP-1 injection for weight management, while Mounjaro (tirzepatide) works on both GLP-1 and GIP pathways for a dual effect. Both medications work similarly:
- Signal your brain's appetite control centres that you feel full
- Slow how quickly food moves through your stomach
- Reduce food cravings and thoughts about eating
- Help regulate blood sugar and fat metabolism
In clinical trials, patients on Wegovy reported significantly reduced hunger and food preoccupation by week 4, with effects strengthening over the following weeks. The appetite reduction typically increases as your dose increases — starting at 0.25 mg with Wegovy and 2.5 mg with Mounjaro, with gradual weekly escalation.
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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.
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What to Expect With Decreased Appetite
When appetite decreases on a GLP-1 medication, you may notice you feel satisfied after eating much smaller portions, need to remind yourself to eat, or find that foods you previously enjoyed feel less appealing. This typically feels natural rather than restrictive — you're simply less interested in food. Many patients report this makes weight management feel less mentally exhausting because constant hunger and food preoccupation fade significantly.
However, this reduced appetite works best alongside a reduced-calorie diet and increased physical activity — medication is a tool, not a complete solution on its own. Track your progress using our free progress tracker, and use our GLP-1 weight loss calculator to explore potential outcomes at different doses. Always work with your prescriber if appetite suppression feels extreme or you're struggling to eat enough.
- 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.
Does decreased appetite from weight loss medication feel uncomfortable?
No — most patients describe it as a natural shift rather than an unpleasant sensation. You simply feel satisfied with smaller meals and think about food less often. Some patients initially worry they won't eat enough, but appetite naturally stabilises at a level that supports your health.
Why do GLP-1 medications decrease appetite?
GLP-1 is a natural gut hormone that signals fullness to your brain. Prescription GLP-1 medications like Wegovy amplify this signal, which tells your brain you're satisfied sooner and reduces hunger hormones like ghrelin. This is a biological mechanism, not chemical suppression.
How quickly does appetite decrease on Wegovy or Mounjaro?
Most patients notice reduced appetite within the first 1–2 weeks at starting doses. As you increase your dose every 4 weeks, appetite suppression typically strengthens further. Maximum effect usually occurs once you reach your maintenance dose (2.4 mg Wegovy or up to 15 mg Mounjaro).
What if my appetite doesn't decrease on weight loss medication?
Individual responses vary — some patients experience stronger appetite reduction than others. Your prescriber may adjust your dose or explore whether timing of meals or food composition affects your response. A GP or specialist can help troubleshoot if appetite suppression is insufficient.
Can decreased appetite cause nutritional problems?
Not if you're eating a balanced diet in smaller portions. Focus on nutrient-dense foods (protein, vegetables, whole grains) rather than volume. Your prescriber may recommend monitoring your nutrition, and keeping a food diary helps ensure you're meeting your nutritional needs.
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.