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 Diets: Evidence-Based Approaches for UK Adults
Weight loss diets are a key part of managing your weight and improving your health. The most effective weight management approaches combine dietary changes with increased physical activity, alongside lifestyle adjustments that suit your routine. The NHS recommends losing weight at a sustainable rate of 0.5 to 1 kg per week, which typically requires a calorie deficit of around 500 kcal per day. Several evidence-based diets have been shown to support weight loss when combined with commitment and support. Use our free BMI calculator to establish your current position, then explore which dietary approach might work best for you.
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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 Weight Loss Diet Approaches in the UK
Several weight loss diets are widely used across the UK, each with research support:
- Mediterranean diet: Emphasises olive oil, fish, vegetables, and whole grains. Strong evidence for both weight loss and cardiovascular health benefits. Sustainable long-term approach.
- Low-carbohydrate diet: Reduces bread, pasta, and sugar. Effective for short-term weight loss; long-term outcomes similar to standard calorie restriction.
- Intermittent fasting (5:2 or 16:8): Restricts eating to specific time windows or days. Evidence suggests modest weight loss comparable to traditional dieting.
- Calorie deficit approach: The evidence-based foundation of all diets. A deficit of 500 kcal daily typically results in 0.5 kg weekly loss.
The NHS weight loss pathway recommends starting with Tier 1 self-help and community programmes before considering medication. Any sustainable approach should include both dietary change and increased physical activity. Our free weight loss calculator can help you project potential results based on different approaches, whilst our progress tracker helps you monitor changes over time.
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 to Consider Professional Support and Weight Loss Medication
If dietary changes and exercise alone haven't achieved results, your GP can discuss prescription weight loss medication options. The NHS provides structured weight loss medication nhs through specialist weight management services (Tier 3 and Tier 4). Prescription weight loss injections such as GLP-1 medications may be offered if you have a BMI of 30 or above, or 27 or above with weight-related health conditions. These are used alongside dietary changes, not instead of them. Private prescribing is also available through GPhC-registered online pharmacies following a clinical assessment. Whatever approach you choose — diet alone, combined with exercise, or supported by medication — the goal is sustainable weight loss that improves your long-term health. Our BMI calculator helps you track whether your current weight falls within NHS healthy ranges.
- 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 best weight loss diet for UK adults?
There is no single "best" diet — effectiveness depends on what you can sustain long-term. The Mediterranean diet has strong evidence for health outcomes. Low-carb, intermittent fasting, and standard calorie restriction all produce similar weight loss if followed consistently. The NHS recommends a 500 kcal daily deficit for 0.5–1 kg weekly loss. Consult your GP for personalised advice.
How quickly can I lose weight with a diet?
The NHS recommends 0.5–1 kg per week as a safe, sustainable rate. This typically requires a calorie deficit of 500 kcal daily. Faster loss risks muscle loss and nutrient deficiency. Losing just 5–10% of your body weight can have measurable health benefits, even if further loss is needed.
Can weight loss diets be combined with weight loss medication?
Yes, and they should be. Prescription weight loss medications such as GLP-1 injections (Mounjaro, Wegovy) are designed to be used alongside dietary changes and increased physical activity, not as replacements. Your prescriber will advise on combining medication with your chosen dietary approach.
What if diet and exercise alone aren't working?
If you've lost less than expected after 3–6 months of consistent effort, discuss other options with your GP. Prescription weight loss medication, referral to specialist services, or assessment for underlying conditions (thyroid, PCOS) may be appropriate. Weight is influenced by genetics, medications, and medical conditions — professional support can help identify barriers.
How do I know if a weight loss diet is right for me?
Consider sustainability, cultural fit, and whether it includes whole foods and adequate nutrition. Avoid very restrictive diets (under 1200 kcal daily) without medical supervision. Check your BMI using our free BMI calculator to understand your health baseline, then discuss with your GP which approach suits your lifestyle and medical history best.
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.