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 Training and Weight Loss — What You Need to Know
High-intensity interval training (HIIT) is a form of exercise involving short bursts of intense activity followed by recovery periods. Many people in the UK use HIIT as part of their weight management strategy. However, sustainable weight loss requires a combination of regular physical activity, dietary changes, and in some cases, professional support from your GP. This guide explains how HIIT can support your weight loss goals and how it fits into an overall approach to achieving and maintaining a healthy weight.
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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 Training Supports Weight Loss
HIIT works through several mechanisms that may support weight loss. During high-intensity intervals, your body uses significant energy, which contributes to calorie expenditure. HIIT also increases your metabolic rate for hours after exercise — a process called excess post-exercise oxygen consumption (EPOC). This means your body continues to burn calories even after your workout ends. Additionally, HIIT may help preserve lean muscle mass during weight loss, which is important because muscle tissue burns more calories at rest than fat tissue.
- Typical HIIT sessions last 15–30 minutes, making them time-efficient compared to steady-state cardio
- Research suggests HIIT can improve cardiovascular fitness and blood sugar control
- Regular HIIT may support weight management when combined with a healthy diet and adequate sleep
- HIIT can be adapted to different fitness levels — from beginner-friendly to advanced
For sustainable weight loss, the NHS recommends losing 0.5 to 1 kg per week, which typically requires a calorie deficit of around 500 kcal per day. Exercise is one part of this equation — dietary changes are equally important.
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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.
Combining HIIT with Other Weight Loss Approaches
HIIT works best as part of a comprehensive approach to weight management. This includes reducing calorie intake through dietary changes, staying hydrated, getting adequate sleep, and managing stress. Many people find that combining regular exercise with structured dietary support produces better results than exercise alone.
If you're struggling with weight management despite regular exercise and dietary efforts, your GP can assess your individual situation and discuss options. These may include referral to NHS weight management services or, for eligible adults, prescription weight loss medication. Our free BMI calculator and weight loss calculator can help you understand your current weight status and explore different weight management approaches. Always consult your GP before starting a new exercise programme, especially if you have any existing health conditions.
- 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 often should I do HIIT training for weight loss?
Most evidence suggests 3–4 HIIT sessions per week, combined with other forms of activity and rest days, supports weight management. Consistency matters more than frequency — sustainable exercise habits are more important than intense but sporadic training. Your GP or a fitness professional can advise on what's appropriate for your fitness level.
Can HIIT alone cause weight loss without changing my diet?
HIIT alone is unlikely to cause significant weight loss without dietary changes. Weight loss requires a calorie deficit, which is best achieved through a combination of increased physical activity and reduced calorie intake. The NHS recommends a 500 kcal daily deficit for sustainable loss of around 0.5–1 kg per week.
Is HIIT safe for overweight or obese adults?
HIIT can be adapted for different fitness levels, but overweight or obese adults should consult their GP before starting. Your GP may recommend starting with lower-intensity exercise and gradually progressing. A qualified fitness professional can help you modify exercises to suit your current fitness level safely.
What's the difference between HIIT and regular steady cardio for weight loss?
HIIT typically burns calories more efficiently in shorter timeframes and may increase metabolic rate post-exercise. However, both HIIT and steady cardio support weight loss when combined with dietary changes. The "best" exercise is the one you'll do consistently — choose based on your preferences and fitness level.
Can HIIT help if I'm taking weight loss medication like GLP-1 injections?
Yes, exercise including HIIT is recommended alongside prescription weight loss medication like Mounjaro or Wegovy. These medications work best when combined with dietary changes and increased physical activity. Always discuss any new exercise programme with your prescriber or GP, especially when taking weight loss medications.
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.