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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HIIT and Weight Loss: Does High-Intensity Training Work?
High-intensity interval training (HIIT) is a popular exercise method involving short bursts of intense effort followed by recovery periods. Research suggests HIIT can support weight loss when combined with a healthy diet, though results vary between individuals. The NHS recommends that adults engage in regular physical activity alongside dietary changes for sustainable weight management. This guide explains how HIIT works, its potential benefits, limitations, and how it fits into a comprehensive UK weight loss approach.
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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 HIIT Supports Weight Loss and Energy Expenditure
HIIT sessions typically last 15–30 minutes and involve exercises like sprinting, cycling, or jumping at maximum effort for 20–40 seconds, followed by 1–2 minutes of recovery. This approach increases excess post-exercise oxygen consumption (EPOC) — your body continues burning calories for hours after exercise ends. Studies suggest HIIT may burn more calories per unit of time than steady-state exercise, though total weekly energy expenditure depends on overall activity volume and consistency.
- HIIT elevates heart rate and metabolic rate during and after workouts
- Sessions are time-efficient, making regular exercise more sustainable
- HIIT preserves muscle mass better than low-intensity steady cardio during weight loss
- Individual calorie burn varies based on fitness level, age, body composition, and exercise intensity
However, HIIT alone does not clinically studied weight loss. The NHS emphasises that sustainable weight management requires a calorie deficit — consuming fewer calories than you expend. Exercise supports this, but dietary changes remain essential. The NHS recommends losing weight at approximately 0.5–1 kg per week through a combination of physical activity and healthy eating.
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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.
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HIIT Safety, Limitations, and When to Seek Medical Advice
HIIT is high-impact and demanding on the cardiovascular and musculoskeletal systems. It is not suitable for everyone without medical clearance. Before starting HIIT, consult your GP if you have: high blood pressure, heart disease, joint problems, obesity (BMI 30+), or are recovering from injury.
HIIT benefits are enhanced when combined with consistent dietary changes, adequate rest, and progressive training. Beginners should start with modified versions — longer recovery intervals and lower-impact variations — to reduce injury risk. Use our free BMI calculator above to assess your current weight status and discuss appropriate exercise intensity with your GP. Track your progress with our progress tracker as you combine exercise with lifestyle changes. For sustainable weight management in the UK, the NHS recommends integrating HIIT within a broader routine that includes diet, rest, and activities you enjoy.
- 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.
Can HIIT alone help you lose weight?
HIIT alone is unlikely to produce significant weight loss without dietary changes. Weight loss requires a calorie deficit — burning more calories than consumed. HIIT supports this by increasing energy expenditure, but diet is equally important. The most effective approach combines regular HIIT with healthy eating, adequate sleep, and stress management.
How often should I do HIIT for weight loss?
The NHS recommends 150 minutes of moderate aerobic activity or 75 minutes of vigorous activity (including HIIT) per week. HIIT sessions of 20–30 minutes, performed 2–3 times weekly alongside other activities, can support weight loss. Allow at least one rest day between intense sessions to prevent overtraining and injury.
Is HIIT safe if I'm overweight or obese?
High-intensity exercise carries injury risk if you're overweight or obese, particularly for joints and the cardiovascular system. Always consult your GP before starting HIIT. Modified, low-impact versions may be suitable, or your GP may recommend starting with lower-intensity exercise first. Gradual progression under professional guidance is safer.
Does HIIT burn more calories than steady-state cardio?
HIIT typically burns more calories per minute than steady cardio, and the "afterburn effect" means elevated calorie burn for hours post-exercise. However, total weekly calorie burn depends on overall activity volume and consistency. Many people find HIIT more sustainable due to shorter session times, but the best exercise is one you'll do regularly.
How does HIIT compare to prescription weight loss medication?
HIIT is a lifestyle intervention, while prescription medications like GLP-1 injections work through appetite regulation. Both can support weight loss, but they work differently. Medications require clinical assessment and prescription, while HIIT is accessible but needs consistency and dietary changes. Many people combine both approaches under medical guidance for comprehensive weight management.
Ready to take control of your weight loss journey?
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