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
Liquid Diet for Weight Loss — What You Need to Know
A liquid diet involves consuming mostly or entirely liquid calories — such as soups, smoothies, juices, or meal replacement drinks — instead of solid foods. While liquid diets can support weight loss in the short term, the NHS emphasises that sustainable weight management in the UK requires a balanced approach combining dietary changes with physical activity. This guide covers what liquid diets are, how they work, their effectiveness, and safer alternatives for long-term weight loss success.
10,000+ calculations today · NHS-aligned thresholds · 100% free
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.
How Liquid Diets Work for Weight Loss
Liquid diets typically create a calorie deficit because liquid foods are often lower in calories than solid meals and may leave you feeling fuller due to their volume. Common types include:
- Meal replacement shakes — nutritionally balanced liquid meals designed to replace one or more daily meals
- Juice cleanses — fruit and vegetable juices consumed over several days (not recommended long-term by NHS)
- Broth-based soups — warm, filling, and lower in calories
- Very low-calorie diets (VLCDs) — under 800 kcal daily, only under medical supervision
The NHS recommends a calorie deficit of around 500 kcal per day for sustainable weight loss of approximately 0.5 kg per week. Liquid diets can achieve this, but they work best as part of broader lifestyle changes rather than as a standalone approach. Use our free BMI calculator to understand your starting point, and our weight converter to track progress in stone and kg.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Safety, Sustainability, and Better Alternatives
While short-term liquid diets may produce quick results, they often lack essential nutrients like fibre, certain vitamins, and minerals needed for long-term health. The NHS does not recommend extended liquid-only diets without medical supervision. Most people regain weight after stopping because liquid diets do not teach sustainable eating habits.
For lasting weight management in the UK, the NHS recommends:
- Balanced reduced-calorie diet with whole foods
- Regular physical activity (at least 150 minutes weekly)
- Professional support from your GP or a dietitian
- For eligible adults, prescription weight loss medication alongside lifestyle changes
If you are struggling with weight loss, your GP can discuss options including prescription weight loss injections like GLP-1 medications, which may support sustainable results when combined with diet and exercise. Try our GLP-1 weight loss calculator to explore potential outcomes with medical support.
- 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 you lose weight quickly on a liquid diet?
Yes — liquid diets often produce rapid initial weight loss due to lower calorie intake and reduced food volume. However, much of this is water weight and glycogen depletion, not fat loss. The NHS recommends sustainable loss of 0.5–1 kg per week. gradual weight management is not healthier and often leads to muscle loss and weight regain.
Is a liquid diet safe long-term?
No. Extended liquid diets lack adequate fibre, protein, and micronutrients needed for health. The NHS does not recommend liquid-only diets without medical supervision. If you are considering a very low-calorie liquid diet (under 800 kcal daily), speak to your GP first — it requires professional monitoring.
What's the difference between a liquid diet and a meal replacement shake?
Meal replacement shakes are designed as nutritionally complete liquid foods to replace one meal daily, and many are NHS-approved as part of structured weight management programmes. Full liquid diets replace all solid food. Shakes are safer long-term because they form part of a mixed diet, not the entire diet.
Will I regain weight after a liquid diet?
Most people do, because liquid diets do not teach lasting eating habits. The NHS emphasises that sustainable weight loss requires permanent lifestyle changes — reduced calories, physical activity, and behaviour change — not temporary dietary restrictions. This is why professional support and balanced approaches work better.
Are liquid diets better than weight loss medication?
They work differently. Liquid diets create short-term calorie deficits; prescription weight loss medications (like GLP-1 injections) help regulate appetite and support sustained behaviour change. For the best results, many people combine a balanced diet with medical support if eligible. Your GP can advise what's right for you.
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.