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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How to Work Out Your BMR — UK Health Guide
Your basal metabolic rate (BMR) is the number of calories your body burns at rest — just to keep your heart beating, breathing, and maintaining body temperature. Understanding your BMR is crucial for weight management in the UK, as it forms the foundation of any sustainable healthy weight plan. This guide explains what BMR is, how to calculate it, and how it relates to your overall health and fitness goals.
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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.
BMR Calculation Methods — Step-by-Step
The most common method for calculating BMR is the Mifflin-St Jeor equation, which is more accurate than older formulas. You'll need your weight (in kg), height (in cm), age (in years), and biological sex.
For men: BMR = (10 × weight) + (6.25 × height) − (5 × age) + 5
For women: BMR = (10 × weight) + (6.25 × height) − (5 × age) − 161
Example: A 35-year-old woman weighing 70kg and 165cm tall would calculate: (10 × 70) + (6.25 × 165) − (5 × 35) − 161 = 1,413 calories per day.
The older Harris-Benedict equation exists but tends to overestimate BMR slightly. For most UK health guidance purposes, Mifflin-St Jeor is recommended by nutritionists and aligns with NHS weight management principles.
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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
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BMR vs TDEE — Why the Difference Matters
Your BMR is what you burn doing nothing. Your TDEE (total daily energy expenditure) is how many calories you actually burn with daily activity included. To estimate TDEE, multiply your BMR by an activity factor: sedentary (1.2), lightly active (1.375), moderately active (1.55), very active (1.725), or extremely active (1.9).
For weight loss, the NHS recommends a calorie deficit of around 500 calories daily, creating roughly 0.5kg weekly loss. Knowing your BMR and TDEE helps you set realistic targets aligned with NHS weight management guidance and avoid crash dieting.
- 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 a typical BMR for UK adults?
Average BMR varies by age, sex, and body composition. A typical adult woman has a BMR around 1,200–1,400 calories daily; men typically 1,500–1,800 calories. Muscle tissue burns more calories at rest, so more muscular individuals have higher BMR. Use our free BMI calculator to assess your healthy weight range first.
Does BMR change with age or weight loss?
Yes. BMR naturally decreases by approximately 2–8% per decade after age 30 due to muscle loss. During weight loss, BMR may drop slightly as your body has less mass to maintain. This is why UK health guidance emphasises combining diet with strength-building activity to preserve muscle.
Can I use BMR to plan weight loss in the UK?
Yes. Calculate your BMR, multiply by your activity factor to get TDEE, then subtract 500 calories for safe weekly loss of approximately 0.5kg. The NHS recommends this gradual approach. For personalised advice, discuss your targets with your GP or a registered dietitian.
Is BMR the same as metabolic rate?
No. BMR is calories burned at complete rest. Resting metabolic rate (RMR) is similar but measured under less strict conditions. For practical UK weight management, both are used interchangeably, though BMR is technically more precise.
Should I use BMR when taking weight loss medication?
If you're prescribed Mounjaro, Wegovy, or other weight loss medication, your prescriber will consider your overall calorie needs. BMR calculation helps establish a baseline, but medication changes how your body regulates appetite. Always discuss diet and activity with your prescriber alongside any medication.
Ready to take control of your weight loss journey?
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