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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Diet Programs for Weight Loss in the UK
Losing weight effectively requires a structured approach that works for your lifestyle. In the UK, weight loss support ranges from self-managed diet programs to NHS-supervised schemes and prescription weight loss medication. This guide covers evidence-based diet programs, how they compare, and what the NHS recommends. Understanding your options — from calorie-deficit approaches to specialist weight management services — helps you choose a sustainable path forward. Check your personal health context using our free BMI calculator above to see where you currently stand.
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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 Diet Programs and Evidence-Based Approaches
Several diet programs for weight loss are widely used across the UK, each with evidence supporting modest weight loss when combined with physical activity:
- Calorie-deficit dieting: A 500 kcal daily deficit typically results in approximately 0.5 kg weight loss per week. This remains the most evidence-backed approach. Our free weight converter and BMI calculator help you track your baseline and monitor progress.
- Mediterranean diet: Strong evidence supports cardiovascular health and sustainable weight management, with average weight loss of 5–10% over 12 months.
- Intermittent fasting (16:8, 5:2): Evidence suggests similar weight loss to standard calorie restriction when sustained.
- Low-carbohydrate diets: Effective short-term, though long-term results match standard calorie restriction.
- NHS Weight Loss Plan: Free digital programme available through the NHS, offering guided support at tier 1 of the NHS weight management pathway.
The NHS emphasises that sustainable weight loss in the UK should aim for 0.5–1 kg per week alongside increased physical activity.
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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.
NHS Weight Loss Support and Prescription Options
The NHS weight loss pathway offers tiered support. Tier 1 includes self-help and digital tools. Tier 2 provides primary care-based behaviour change programmes. Tier 3 is specialist multidisciplinary weight management services — where prescription weight loss UK options may be introduced. Prescription weight loss medication for eligible adults includes GLP-1 injections like Wegovy and dual GIP/GLP-1 options like Mounjaro. Our GLP-1 weight loss calculator can help estimate potential outcomes at different doses. These medications work alongside diet changes, not instead of them. Eligibility requires a BMI of 30+ or 27+ with weight-related health conditions. Access varies by region — some areas have longer waiting lists than others. Many people combine structured diet programs with prescription support for better results.
- 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 is the most effective diet program for weight loss?
Evidence suggests calorie-deficit dieting (500 kcal/day deficit) is most reliable, producing approximately 0.5 kg weekly loss. Mediterranean and intermittent fasting approaches also have good evidence. The most effective program is the one you can sustain long-term alongside physical activity. Your GP can advise which suits your lifestyle.
Can I access weight loss medication through the NHS?
Yes. NHS specialist weight management services (tier 3) may prescribe medications like Wegovy or Mounjaro for eligible adults with a BMI of 30+ or 27+ with weight-related health conditions. Availability and waiting times vary by region. Ask your GP about local services.
How quickly should I expect to lose weight on a diet program?
The NHS recommends losing 0.5–1 kg (1–2 lbs) per week for sustainable, healthy weight loss. Faster loss increases muscle loss risk. Very gradual weight management (>1.5 kg/week) should only be done under medical supervision.
What is the difference between diet alone and diet plus weight loss medication?
Diet creates the calorie deficit needed for weight loss. Prescription weight loss medication (like GLP-1 injections) helps reduce appetite and support feeling fuller, making the calorie deficit easier to maintain. Medications are used alongside diet and exercise, not as a replacement.
How do I know which diet program is right for me?
Consider your lifestyle, food preferences, and health conditions. Start by checking your BMI using our free calculator above. Then speak with your GP, who can assess your individual health context and recommend tier-appropriate support — from self-help digital tools to specialist services.
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.