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
Free tracker included with every download this week
Good Diets For Weight Loss — What Works in the UK
Sustainable weight loss starts with the right diet approach paired with lifestyle changes. In the UK, the NHS recommends a calorie deficit of around 500 kcal per day for steady, sustainable weight loss of approximately 0.5 to 1 kg per week. The best diets for weight management aren't restrictive crash diets — they're approaches you can maintain long-term whilst still enjoying food. Whether you're looking for NHS weight loss support or exploring options like prescription weight loss medication, understanding which diet suits your lifestyle is the first step. Use our free BMI calculator above to see where you stand, then explore evidence-based approaches below.
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Calculate Your BMI Instantly
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.
Evidence-Based Diets That Support Weight Loss
Mediterranean diet: Strong NHS evidence supports this approach. Focus on olive oil, fish, vegetables, whole grains, and legumes. Associated with cardiovascular health and sustainable weight loss when combined with calorie awareness.
Low-calorie structured diet: Typically 1,200–1,500 kcal per day for women, 1,500–1,900 kcal for men. Requires tracking but delivers consistent results. The NHS Weight Loss Plan offers free structured guidance.
Intermittent fasting (16:8 or 5:2): Evidence shows modest weight loss comparable to standard calorie restriction. 16:8 means eating within an 8-hour window; 5:2 means eating normally 5 days, restricting calories 2 days. Works best if you can maintain it long-term.
Low-carbohydrate approaches: Effective short-term; long-term results are similar to calorie restriction. Popular in UK weight management programmes but requires sustained commitment.
All these diets work best when combined with increased physical activity and supported by a prescriber if using prescription weight loss medication like Mounjaro or Wegovy alongside diet changes.
Clinically BackedWeight Loss
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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.
Combining Diet With Weight Management Support
Diet alone is powerful, but the NHS weight management pathway shows that outcomes improve significantly when diet is combined with behaviour change support and, where eligible, prescription medication. If you have a BMI of 30 or above, or 27 or above with weight-related health conditions like type 2 diabetes or high blood pressure, you may be eligible for specialist NHS weight loss support or private prescription options.
Our GLP-1 weight loss calculator can help you understand potential weight loss with medication combined with diet changes. Whatever approach you choose, the key is consistency: aim for a steady deficit of 500 kcal per day, track progress using our free progress tracker, and remember that individual results vary. Consult your GP about the best approach for your personal health needs.
- 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.
What's the best diet for quick weight loss in the UK?
The NHS recommends losing 0.5–1 kg per week for sustainable results rather than rapid loss. Crash diets rarely work long-term. A calorie deficit of 500 kcal per day through balanced diet and activity is safer and more effective. For faster results with medical support, prescription weight loss medication combined with diet changes may be appropriate — discuss eligibility with your GP.
Can I lose weight with diet alone, or do I need medication?
Many people achieve weight loss through diet and activity changes alone. However, if you've tried lifestyle changes without success, or have a BMI over 30 with health conditions, prescription weight loss medication may help. These medications work alongside diet, not instead of it. Your GP or a licensed prescriber can assess whether medication is suitable for you.
How does the Mediterranean diet help with weight loss?
The Mediterranean diet emphasises whole foods — fish, vegetables, olive oil, legumes, and whole grains — naturally lower in processed calories. It supports sustained weight loss when combined with calorie awareness, and has strong NHS evidence for cardiovascular health. It's sustainable because you're not eliminating food groups, just focusing on quality.
What's the difference between intermittent fasting and calorie restriction?
Both create a calorie deficit, just in different ways. Calorie restriction limits total daily calories; intermittent fasting limits eating to specific time windows (like 16:8). Evidence shows weight loss outcomes are similar. Choose whichever fits your lifestyle better — the best diet is one you can stick to long-term.
Should I use a diet plan alongside weight loss injections like Mounjaro or Wegovy?
Yes. Prescription weight loss medications work best alongside a reduced-calorie diet and increased physical activity. Clinical trials show these medications support appetite control, but diet and lifestyle changes remain essential. Your prescriber will discuss this during your clinical assessment.
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.