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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High Intensity Exercise for Weight Loss
High intensity exercise (HIIT) can be an effective tool for weight loss, helping you burn significant calories in shorter workout sessions. Combined with a reduced-calorie diet and lifestyle changes, high intensity training supports sustainable weight management. The NHS recommends both aerobic activity and strength training as part of a healthy weight loss plan. This guide explains how HIIT works, what the evidence shows, and how to use it safely as part of your weight loss journey in the UK.
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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.
How High Intensity Exercise Works for Weight Loss
High intensity interval training (HIIT) alternates between short bursts of maximum effort exercise and recovery periods. This approach burns more calories in less time compared to steady-state cardio — a process called the "afterburn effect" or excess post-exercise oxygen consumption (EPOC). Your body continues burning calories at an elevated rate even after you finish exercising.
- HIIT typically involves 20–30 second intense efforts followed by rest or lower intensity recovery
- Sessions are usually 15–30 minutes total, including warm-up and cool-down
- Evidence shows HIIT can burn 25–30% more calories per minute than traditional steady-state exercise
- Regular HIIT also supports improved cardiovascular fitness and insulin sensitivity
For sustainable weight loss in the UK, the NHS recommends combining exercise with a calorie deficit of around 500 kcal per day, which typically results in losing approximately 0.5–1 kg per week. Try our free BMI calculator above to check your current starting point, then use our weight loss calculator to see how different lifestyle changes may affect your progress.
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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.
HIIT Safety and Getting Started
High intensity exercise requires gradual progression to prevent injury. If you're new to exercise, start with lower intensity workouts and build up over several weeks. Always warm up properly and cool down after each session.
- Speak to your GP before starting HIIT if you have joint problems, heart conditions, or are significantly overweight
- Wear supportive trainers and choose low-impact options (cycling, rowing, swimming) if you have knee or ankle concerns
- Combine HIIT with at least 2 days per week of strength training for best results
- Stay hydrated and fuel your body properly — exercise alone without dietary changes rarely produces sustained weight loss
For comprehensive weight management UK support, the NHS recommends combining exercise with dietary changes. Track your progress using our free progress tracker to stay motivated and monitor what's working for you.
- 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.
How many calories does high intensity exercise burn?
A 30-minute HIIT session can burn 250–400 calories depending on your weight, fitness level, and exercise intensity. HIIT burns more calories per minute than steady cardio. However, weight loss ultimately depends on creating a calorie deficit through both exercise and diet combined.
How often should I do HIIT for weight loss?
The NHS recommends at least 150 minutes of moderate activity or 75 minutes of vigorous activity per week. HIIT can count toward vigorous activity. Most people benefit from 2–3 HIIT sessions per week, combined with other types of exercise and strength training.
Can HIIT alone lead to weight loss?
Exercise alone, including HIIT, is less effective than combining it with dietary changes. For sustainable weight loss, you need a calorie deficit — typically 500 kcal per day for approximately 0.5–1 kg per week loss. Diet accounts for roughly clinically studied weight loss success.
Is HIIT safe for people with obesity?
High intensity exercise can be challenging for people carrying significant excess weight due to joint stress. Start with lower impact options like swimming or cycling, build fitness gradually, and speak to your GP first. Combining exercise with structured weight management — including prescription options like GLP-1 weight loss medication if appropriate — may be more effective initially.
What's the difference between HIIT and steady cardio for weight loss?
HIIT burns more calories in less time and creates a longer "afterburn effect," but both are effective for weight loss. The best approach is whichever you'll stick with consistently, combined with dietary changes. The NHS recommends including both cardiovascular exercise and strength training as part of a balanced fitness routine.
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.