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
Best Diet Plans for Weight Loss in the UK
There's no single "best" diet plan for weight loss — what works depends on your lifestyle, preferences, and health. The NHS recommends sustainable approaches that combine dietary changes with increased physical activity, aiming for a weight loss of 0.5–1 kg per week. This guide explores evidence-based diet plans available in the UK, from calorie-controlled approaches to Mediterranean eating patterns, plus how prescription weight loss medication may support your goals alongside dietary changes. Use our free BMI calculator to establish your baseline, and track your progress as you find the approach that suits you best.
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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.
Popular Evidence-Based Diet Plans for Weight Loss
Calorie deficit approach: Creating a deficit of approximately 500 kcal per day typically results in losing around 0.5 kg weekly. This is the fundamental principle behind most successful weight loss.
- Mediterranean diet: High in vegetables, olive oil, fish, and whole grains. Strong evidence supports this for sustainable weight management and cardiovascular health.
- Low-carbohydrate diet: Restricts carbs to 20–50g daily. Effective short-term, though long-term results are similar to standard calorie restriction.
- Intermittent fasting (16:8): Eating window of 8 hours, fasting for 16. Emerging evidence suggests modest benefits, though adherence is key.
- 5:2 diet: Normal eating 5 days, reduced intake (500–600 kcal) on 2 non-consecutive days. Moderate evidence for effectiveness.
The "best" plan is whichever you can sustain long-term whilst maintaining nutritional balance.
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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.
Weight Loss Medication and Diet: Working Together
For adults with a BMI of 30 or above, or 27 and above with weight-related health conditions, prescription weight loss medication may support dietary efforts. GLP-1 medications like Wegovy (semaglutide) are available through NHS weight management services or private prescribing in the UK. These medications work by reducing appetite and supporting portion control — they're most effective when combined with a reduced-calorie diet and increased activity.
Our GLP-1 weight loss calculator can help you estimate potential weight loss at different doses when used with dietary changes. Always consult your GP to discuss which approach — dietary, medication, or combined — suits your individual circumstances and health profile best.
- 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 plan for weight loss?
There's no single best plan — it depends on your preferences and lifestyle. The NHS recommends any approach that creates a calorie deficit and can be sustained long-term. Mediterranean, low-carb, and intermittent fasting all have evidence supporting them. The most effective diet is the one you'll stick to.
How much weight can I expect to lose with a diet plan?
The NHS recommends losing 0.5–1 kg per week for sustainable results. A calorie deficit of around 500 kcal daily typically achieves this. Results vary based on starting weight, metabolism, adherence, and exercise. Use our free progress tracker to monitor your journey.
Should I use a diet plan with prescription weight loss medication?
Prescription medications like Wegovy are most effective alongside dietary changes, not as a replacement. They reduce appetite and support portion control, making a reduced-calorie diet easier to follow. Your GP or prescriber can assess whether medication is suitable for you.
How do I know what weight is healthy for me?
The NHS BMI calculator is a good starting point. A healthy BMI is 18.5–24.9 for most adults, or 18.5–22.9 for South Asian, Chinese, Black African, and Black Caribbean adults. Use our free BMI calculator to check your personal range and discuss targets with your GP.
Is very gradual weight management safe?
The NHS advises against losing more than 1–2 lbs per week without medical supervision. Faster weight loss increases risk of muscle loss, nutrient deficiency, and fatigue. Sustainable, gradual weight loss is safer and more likely to be maintained long-term.
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.