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
Weight Loss Diet Plans — What Works in the UK
There's no single "best" diet plan — effective weight loss depends on finding an approach you can sustain. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week through a combination of reduced-calorie eating and increased physical activity. This guide covers evidence-based diet approaches used across the UK, from calorie deficit methods to structured programmes, alongside information about prescription weight loss medication. Use our free BMI calculator to establish your starting point, and our weight loss calculator to understand what realistic progress looks like.
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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 Diet Approaches for Weight Management
Calorie deficit is the foundation of any weight loss plan. To lose approximately 0.5 kg per week, you need a deficit of around 500 kcal per day. Most UK adults need between 1,500–2,000 kcal daily to achieve steady weight loss. The NHS Weight Loss Plan offers a structured 12-week programme combining diet and activity tracking.
- Low calorie diet (LCD): 800–1,200 kcal/day — effective but requires supervision and often results in rapid initial weight loss
- Mediterranean diet: Emphasises whole grains, vegetables, olive oil, and lean protein — backed by strong evidence for both weight management and cardiovascular health
- Intermittent fasting (16:8, 5:2): Restricts eating to specific windows or days — can help some people maintain a calorie deficit more naturally
- Low carbohydrate approaches: Effective for initial weight loss; long-term outcomes similar to standard calorie restriction when total calories are controlled
Sustainable weight loss within NHS weight management UK programmes typically combines dietary change with increased physical activity—aiming for at least 150 minutes of moderate activity weekly.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
When Diet Alone Isn't Enough — Medical Support Available
If diet and lifestyle changes alone haven't produced the results you need, prescription weight loss medication may be an option. GLP-1 weight loss injections like Wegovy or Mounjaro, alongside a reduced-calorie diet, have shown significant results in clinical trials. These are prescription-only medications requiring a clinical assessment. In the UK, you can access them through NHS specialist weight management services (tier 3) or via private prescription after online assessment. Our GLP-1 weight loss calculator can help you understand potential outcomes at different doses. Your GP can discuss whether prescription weight loss medication is suitable for your individual circumstances, or you can seek a private clinical assessment.
- 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 safest rate of weight loss?
The NHS recommends losing 0.5 to 1 kg (1–2 lbs) per week. This pace is sustainable and reduces muscle loss. Faster weight loss is possible with medical support but increases the risk of nutrient deficiencies and muscle breakdown. Very rapid loss requires medical supervision.
Do I need to follow a specific diet plan to lose weight?
No single plan works for everyone. The most effective diet is one you can stick to long-term. Whether you choose calorie counting, intermittent fasting, or a structured programme like the NHS Weight Loss Plan, consistency matters more than the specific method. Focus on finding an approach that fits your lifestyle.
How can I calculate my calorie deficit?
Use our free BMI calculator to establish your baseline. A typical deficit of 500 kcal daily creates approximately 0.5 kg weekly loss. Your personal calorie needs depend on age, sex, activity level, and current weight—a GP or dietitian can help you determine your specific targets.
What role do weight loss injections play in a diet plan?
Prescription weight loss medications like Mounjaro or Wegovy work alongside diet and exercise, not instead of them. They may help reduce appetite and cravings, making it easier to maintain a calorie deficit. Clinical trials showed average weight loss of 15–21% with medication plus lifestyle changes—results vary individually.
Can I access weight loss medication through the NHS?
Yes, GLP-1 medications are available through NHS specialist weight management services (tier 3), though availability and waiting times vary by region. Private prescription is also available through UK-licensed prescribers following an online assessment. Your GP can discuss your options or refer you 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.