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
What Is a Fitness Assessment and Why Does It Matter?
A fitness assessment is a comprehensive evaluation of your physical health and exercise capacity. Unlike weight alone, fitness assessments measure cardiovascular endurance, muscle strength, flexibility, and body composition — giving you a fuller picture of your overall health. NHS health advice emphasises that fitness and weight are both important for wellbeing. Whether you're starting a weight management programme or simply want to understand your current fitness level, a proper assessment provides a baseline to track progress over time.
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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.
Types of Fitness Assessment Used in the UK
Cardiovascular fitness tests measure how efficiently your heart and lungs work during exercise. Common tests include the multi-stage fitness test (bleep test), treadmill running tests, and cycle ergometer tests that measure VO2 max — the maximum amount of oxygen your body can use during intense exercise. Strength and power assessments evaluate muscle function using grip strength tests, vertical jump tests, and resistance exercises. Flexibility testing measures range of motion using tests like the sit-and-reach test. Body composition analysis goes beyond weight and BMI to measure fat mass, muscle mass, and bone density using methods such as DEXA scans, bioelectrical impedance analysis (BIA), or skin fold measurements. Many NHS health advice programmes and private fitness centres in the UK now offer these assessments as part of weight management or fitness coaching services.
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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.
How Fitness Assessment Relates to Weight Management
A fitness assessment is particularly valuable if you're considering weight management interventions like lifestyle changes, dietary adjustments, or prescription weight loss support. Understanding your current fitness level helps your GP or healthcare provider tailor recommendations to your specific needs. For example, someone with a healthy BMI but low cardiovascular fitness may benefit from different advice than someone with overweight and excellent fitness levels. You can use our free BMI calculator to assess your weight status, and a fitness assessment complements this by revealing how your body actually functions during physical activity. This combined approach — measuring both weight metrics and fitness capacity — gives you the most complete picture of your health.
- 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 VO2 max and why does it matter?
VO2 max measures the maximum amount of oxygen your body can use during intense exercise, measured in millilitres of oxygen per kilogram of body weight per minute (ml/kg/min). It's a key indicator of cardiovascular fitness and aerobic endurance. Higher VO2 max generally correlates with better heart health and fitness capacity.
Can I get a fitness assessment on the NHS?
Some NHS services offer fitness assessments through specialist weight management services, cardiac rehabilitation programmes, and occupational health referrals. Availability varies by region. Private fitness centres, gyms, and personal trainers throughout the UK also offer comprehensive fitness assessments for a fee.
How does body composition differ from BMI?
BMI measures weight relative to height but doesn't distinguish between muscle and fat. Body composition analysis reveals the actual percentage of fat, muscle, and bone. Someone with high muscle mass may have a high BMI but low body fat. Our free BMI calculator and weight converter help contextualise your weight, but a fitness assessment provides deeper insights into your actual body composition.
How often should I get a fitness assessment?
For general health monitoring, an annual assessment is reasonable. If you're actively involved in a weight management programme or training for sports, assessments every 6–12 weeks can track progress and guide adjustments to your fitness or dietary plan.
Who should perform a fitness assessment?
Qualified professionals including NHS physiotherapists, REPS UK-accredited personal trainers, exercise physiologists, and clinical exercise specialists can conduct fitness assessments. Your GP can refer you to NHS services, or you can book private assessments through accredited fitness providers in your area.
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.