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
Weight Loss and Fat Loss Diet — What Works
Losing weight and reducing body fat requires understanding the difference between weight loss and fat loss, combined with sustainable dietary changes. A calorie deficit is the foundation of weight loss, but the quality of your diet matters for preserving muscle and achieving lasting results. This guide explains the science of weight loss UK approaches, dietary strategies recommended by the NHS, and how prescription weight loss medication fits alongside lifestyle changes.
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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.
Understanding Calorie Deficit and Fat Loss
Weight loss happens when you consume fewer calories than your body burns, creating a calorie deficit. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week, which typically requires a deficit of around 500 kcal per day. A deficit of 1,000 kcal per day may result in faster loss but increases the risk of muscle loss and nutritional deficiency.
Fat loss specifically refers to reducing body fat while preserving muscle mass. This requires three elements: calorie deficit, adequate protein intake (1.6–2.2g per kg body weight), and resistance exercise. Simply cutting calories without exercise or protein can result in muscle loss alongside fat loss, which is why diet quality matters as much as calorie quantity.
Use our free BMI calculator to understand your starting point and healthy weight range. Our GLP-1 weight loss calculator can help you explore how prescription weight loss medication combined with diet might support your specific goals.
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.
Diet Approaches Supported by Evidence
The Mediterranean diet has strong NHS and clinical evidence for sustainable weight management and cardiovascular health. Low-carbohydrate diets can be effective for short-term loss but long-term outcomes are similar to standard calorie-restricted approaches. Intermittent fasting (16:8 or 5:2 patterns) works for some people by naturally reducing eating windows, though it's not superior to regular calorie restriction for most.
For individuals struggling with appetite control or significant weight loss needs, prescription weight loss medication such as GLP-1 injections may be appropriate alongside dietary changes. Weight management UK services often use a combination approach: dietary support, increased physical activity, behavioural strategies, and in some cases, prescription weight loss medication for those who meet NHS eligibility criteria.
- 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.
What's the difference between weight loss and fat loss?
Weight loss includes water, muscle, and fat. Fat loss specifically targets body fat while preserving muscle. To maximise fat loss, combine calorie deficit with adequate protein (1.6–2.2g per kg) and resistance exercise. BMI tells you about overall weight; body fat percentage and waist measurement give a clearer picture of fat loss specifically.
How quickly can I lose weight safely?
The NHS recommends losing 0.5 to 1 kg per week, requiring roughly a 500 kcal daily deficit. Faster loss is possible but increases risk of muscle loss, fatigue, and nutritional deficiency. Sustainable loss at this rate is more likely to be maintained long-term. Your GP can advise on safe approaches for your individual health.
Can diet alone achieve significant fat loss?
Yes, diet creates the calorie deficit required for fat loss. However, adding resistance exercise helps preserve muscle mass during weight loss and improves body composition. The combination of calorie deficit plus adequate protein plus exercise produces the best fat loss outcomes with minimal muscle loss.
When should I consider prescription weight loss medication?
Prescription weight loss injections like Wegovy (semaglutide) may be appropriate for adults with a BMI of 30 or above, or 27–29.9 with weight-related health conditions, following clinical assessment. These medications support appetite control and may aid weight loss alongside diet and exercise—they're not alternatives to lifestyle change.
How do I know if my weight loss plan is working?
Track not just the scales but also body measurements, how clothes fit, and energy levels. Use our free progress tracker to log weekly weight changes. Aim for 0.5–1 kg per week. If you're not losing weight after 4–6 weeks, adjust calorie intake or activity level, or discuss with your GP or a weight loss medication NHS service.
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.