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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4:3 Weight Loss Plan — How It Works in the UK
The 4:3 weight loss plan is a structured eating pattern where you eat normally for four days and restrict calories for three days each week. This approach aims to create a weekly calorie deficit without requiring daily restriction. Like other weight management strategies in the UK, evidence suggests it may help with sustainable weight loss when combined with physical activity and healthy eating habits. However, results vary significantly between individuals, and consulting your GP before starting any new diet plan is always recommended.
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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 the 4:3 Plan Works and Expected Results
The 4:3 weight loss plan divides your week into eating and restriction phases. On four days, you consume normal meals and portions; on three non-consecutive days, you follow a reduced-calorie diet (typically 500–800 calories). This intermittent approach may help some people maintain energy and social eating while creating a meaningful calorie deficit.
- Weekly structure: 4 normal eating days + 3 restricted days
- Restriction days: usually spread across the week (e.g., Monday, Wednesday, Friday)
- Target deficit: approximately 1,500–2,400 calories per week (roughly 0.2–0.3 kg loss)
- Expected weight loss: varies by individual, current weight, and adherence
The NHS recommends a sustainable weight loss rate of 0.5–1 kg per week. The 4:3 plan may achieve this if the normal eating days involve balanced nutrition and appropriate portions. Try our free weight converter to track weight loss in kg, stone, and lbs—the units you use matter when monitoring progress. For a personalised estimate of where your current weight sits in terms of health markers, use our free BMI calculator to establish your baseline.
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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
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Does the 4:3 Plan Compare to Other Weight Management Approaches?
The 4:3 plan is one type of intermittent eating pattern. It differs from daily calorie restriction, which requires consistent reduction every day, and from more intensive approaches like very low-calorie diets (under 800 calories daily), which are only appropriate under medical supervision.
- vs. Daily calorie deficit: 4:3 may be easier psychologically but requires strict adherence on restriction days
- vs. 5:2 intermittent fasting: Similar principle but 5:2 uses two restriction days per week instead of three
- vs. prescription weight loss treatment: GLP-1 medications like Wegovy may offer more consistent results for eligible adults, supported by clinical evidence
For adults with a BMI of 30 or above (or 27 with weight-related health conditions), prescription weight management options exist. Our GLP-1 weight loss calculator can help you explore projected results with medical treatment, though this requires prescription and clinical assessment from a GP or licensed prescriber.
- 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.
Is the 4:3 weight loss plan effective?
Evidence suggests intermittent eating patterns like 4:3 may support weight loss when combined with healthy eating on normal days and physical activity. However, results vary significantly. The key is whether the calorie deficit created across the week is sufficient and sustainable for you personally. Your GP can advise whether this approach suits your health circumstances.
How much weight can I expect to lose on a 4:3 plan?
This depends on your starting weight, metabolism, activity level, and adherence. If the plan creates a calorie deficit of 500–1,500 per week, you might expect loss of roughly 0.1–0.2 kg per week. The NHS recommends aiming for 0.5–1 kg per week for sustainable results, so the 4:3 plan alone may be slower than other approaches.
Is 4:3 safer than daily calorie restriction?
Both approaches are generally safe for most adults, but "safer" depends on your individual health. Some people find intermittent patterns easier to sustain; others struggle with restriction days. gradual weight management (over 1.5 kg per week) increases muscle loss risk. Always consult your GP, especially if you have diabetes, take medications, or have a history of disordered eating.
Can I combine the 4:3 plan with prescription weight loss medication?
Prescription weight management medications like Mounjaro or Wegovy are always used alongside lifestyle changes, including structured eating patterns. However, combining approaches should only be done under medical supervision. Your prescriber will advise whether the 4:3 plan works with your treatment plan.
What should I eat on the four normal days of the 4:3 plan?
"Normal" eating still means balanced nutrition—not unrestricted high-calorie foods. Focus on lean proteins, vegetables, whole grains, and healthy fats. Portion sizes still matter. The overall weekly calorie balance determines weight loss, not just the restriction days. A GP or registered dietitian can provide personalised guidance.
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.