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
Diet Tips For Weight Loss — Evidence-Based UK Guidance
Losing weight sustainably requires more than willpower — it's about understanding how to create a calorie deficit, make lasting dietary changes, and adopt habits that support long-term weight management. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for best results. Whether you're managing your weight alone or alongside prescription weight loss medication, these evidence-based diet tips can help you achieve your goals. Use our free BMI calculator above to understand where you stand, and track your progress as you implement these strategies.
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Calculate Your BMI Instantly
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.
The Foundation: Understanding Calorie Deficit and Portion Control
Weight loss happens when you consume fewer calories than your body burns — this is called a calorie deficit. A deficit of around 500 calories per day typically results in losing approximately 0.5 kg per week. This doesn't mean counting every calorie obsessively, but rather being mindful of portion sizes and making informed choices.
- Use smaller plates to naturally reduce portion sizes without feeling deprived
- Eat protein with every meal — it keeps you fuller longer and preserves muscle during weight loss
- Fill half your plate with vegetables — they're low in calories but high in fibre and nutrients
- Drink water before meals to help with satiety and avoid confusing thirst with hunger
- Be honest about liquid calories: alcohol, sugary drinks, and even "healthy" smoothies add up quickly
The key is sustainability. Extreme restriction leads to burnout and rebound weight gain. Aim for a dietary approach you can stick with for months, not weeks. Many people find success with a balanced, moderate approach rather than eliminating entire food groups.
Clinically BackedWeight Loss
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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.
Practical Dietary Strategies for Sustainable Weight Loss
Beyond calorie counting, what you eat matters for adherence and health. The Mediterranean diet has strong evidence for both weight management and cardiovascular health. Intermittent fasting (such as the 16:8 method) works for some people, though it's not superior to regular calorie restriction — the best diet is the one you'll actually follow.
- Plan meals ahead to avoid impulsive, calorie-dense choices
- Keep a food diary or use a tracking app to build awareness without obsession
- Include foods you enjoy — restriction breeds resentment and failure
- Eat slowly and mindfully — it takes 20 minutes for your brain to register fullness
If you're using prescription weight loss medication as part of your weight management strategy, these diet principles remain essential. Weight loss injections like GLP-1 weight loss medications work best alongside dietary changes and increased physical activity, not as a replacement for them.
- 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 should I eat to lose weight?
The NHS recommends a deficit of around 500 calories per day for safe, sustainable weight loss of 0.5–1 kg weekly. This varies by individual — your GP can provide personalised guidance. Use our BMI calculator to establish your current position, then discuss targets with your healthcare provider. Very low calorie diets (under 800 kcal/day) require medical supervision.
What's the difference between diet and weight management?
A "diet" often implies short-term restriction, whilst weight management is a sustainable long-term approach combining healthy eating, physical activity, and behavioural change. Sustainable weight management focuses on habits you can maintain for life, not quick fixes. The NHS emphasises this distinction in its weight management guidance.
Can I lose weight without cutting calories?
Calorie deficit is the fundamental requirement for weight loss — it's physics, not preference. However, you don't need to obsess over numbers. Eating more protein, fibre, and whole foods naturally reduces calorie intake because these foods are more satiating. Focus on food quality and portions rather than strict counting.
Should I combine diet changes with weight loss medication?
Yes. Prescription weight loss medications like GLP-1 injections work best alongside reduced-calorie diet and increased physical activity — they're not standalone treatments. Medication can help reduce appetite and cravings, making it easier to stick to dietary changes. Your prescriber will discuss this during your clinical assessment.
How long does it take to see weight loss results?
Most people notice changes within 2–4 weeks of consistent dietary changes, though initial loss is often water weight. Fat loss typically becomes apparent around week 4–6. Results vary individually based on starting weight, genetics, metabolism, and adherence. Use our progress tracker to log changes and stay motivated over time.
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.