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
Understanding Body Fat Percentage and Health
Body fat percentage measures the proportion of your weight that is fat tissue, expressed as a percentage of total body weight. Unlike BMI, which doesn't distinguish between muscle and fat, body fat percentage provides a clearer picture of your actual body composition. This UK health guide explains healthy ranges, how it's measured, and why it matters for your overall fitness and health. Our free BMI calculator and weight converter help you assess your weight in context, but understanding body fat gives you more detailed health information.
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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.
Healthy Body Fat Ranges and NHS Guidance
Body fat percentage varies by age and sex. The NHS and fitness professionals use these evidence-based ranges:
- Women: Essential fat 10–13%, Athletic 14–20%, Fitness 21–24%, Acceptable 25–31%, Obese 32%+
- Men: Essential fat 2–5%, Athletic 6–13%, Fitness 14–17%, Acceptable 18–24%, Obese 25%+
Essential fat is the minimum needed for survival and basic body function. Acceptable ranges allow for normal health and daily activity. The NHS emphasises that body fat percentage, combined with waist circumference and BMI, gives a more complete picture of health risk than any single measurement alone. Adults carrying excess fat around the abdomen face higher cardiovascular and metabolic risks, regardless of overall BMI.
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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.
Measuring Body Fat and Using UK Health Tools
Body fat can be measured through several methods: bioelectrical impedance scales (home scales, moderate accuracy), DEXA scans (very accurate, available in some UK hospitals), skinfold callipers (requires trained professional), and underwater weighing (research gold standard, rarely available). For UK adults, use our free BMI calculator to assess your weight category first, then consider body fat measurement if you want more detail. Your GP can advise on whether detailed body composition assessment is appropriate for your health goals. Waist circumference is also simple to measure at home and provides useful health information: men should aim for under 94cm, women under 80cm.
- 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 difference between BMI and body fat percentage?
BMI is calculated from height and weight only, so it cannot distinguish between muscle and fat. Two people with the same BMI may have very different body compositions. Body fat percentage measures actual fat tissue. An athlete might have high BMI but low body fat, while someone with normal BMI might have excess body fat. Use our free weight converter and BMI calculator to check your BMI first, then consider body fat for a fuller picture.
Can I reduce body fat without losing weight?
Yes. If you build muscle through resistance exercise while losing fat, your total weight may stay the same but your body fat percentage decreases. This is why the NHS recommends both aerobic and strength-based activity. You'll feel healthier and your clothes may fit better, even if the scales don't change much. Track your progress using our free progress tracker alongside body composition changes.
What's a healthy waist circumference for UK adults?
According to NHS guidance, men should aim for under 94cm (37 inches) and women under 80cm (31.5 inches). Waist measurement is easy to do at home and is a useful indicator of abdominal fat, which carries higher health risks. If your waist is over 102cm (men) or 88cm (women), the NHS advises speaking to your GP about weight management support.
Is body fat percentage more important than BMI?
Neither is perfect alone. BMI is a useful screening tool but ignores muscle and bone. Body fat percentage shows actual fat tissue but is harder to measure accurately at home. The NHS recommends using both together, plus waist circumference, for a complete health picture. Use our weight converter and BMI calculator to check your starting point, then discuss body composition with your GP.
How often should I measure body fat?
If using home scales, measure monthly to avoid obsessing over daily fluctuations. Monthly checks are enough to track trends. Remember that scales measure weight, not body fat directly. For more accurate body fat measurement, ask your GP about availability on the NHS or through private health assessment. Keep a simple record using our free progress tracker for motivation and accountability.
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.