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
What is the 5+1 Diet Plan — UK Health Guide
The 5+1 diet is a weight management approach where you eat a normal, balanced diet for five days a week and restrict calories significantly on just one or two designated days. This intermittent eating pattern has gained popularity as a sustainable UK health guide for weight loss. The approach aligns with NHS guidance on calorie deficit principles, though individual results vary. Before starting any structured diet plan, it's important to check with your GP, particularly if you have existing health conditions or take medications. MyWeightCheck provides free health information tools including our BMI calculator to help you understand your current weight status within NHS healthy weight UK guidelines.
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 the 5+1 Approach Works for Weight Loss
The 5+1 diet operates on a simple premise: eat normally for five days, then significantly restrict calories (typically to 500–800 kcal) on one or two designated days each week. This creates a weekly calorie deficit without requiring daily restriction.
The mechanism: By maintaining a calorie deficit across the week, you lose weight at approximately 0.5–1 kg per week — aligning with NHS health advice for sustainable weight loss. The flexibility of eating "normally" on non-restricted days may help some people maintain the plan longer than traditional daily calorie restriction.
- Normal eating days: Balanced diet with no specific calorie target, though portion awareness still matters
- Restricted days: Typically 500–800 kcal (very low calorie diet levels — requires GP consideration)
- Weekly deficit: Creates approximately 3,500–7,000 kcal reduction per week
Research suggests this pattern may help preserve metabolic rate better than constant restriction, though evidence is still developing.
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.
5+1 Diet and NHS Weight Management Context
The NHS weight management approach emphasises sustainable, long-term weight loss rather than rapid results. The 5+1 method fits this philosophy by allowing normal eating patterns most days, which may improve adherence compared to restrictive daily diets.
Important considerations: Days involving 500–800 kcal fall into the "very low calorie diet" category, which NHS guidance recommends only under medical supervision. Before starting the 5+1 plan, discuss with your GP if you have diabetes, cardiovascular disease, or take medications affecting appetite or digestion.
Use our free weight converter and BMI calculator to establish your baseline, then track progress weekly. Remember that weight loss is influenced by genetics, sleep, stress, and medical conditions — not diet alone. Combining the 5+1 approach with increased physical activity and adequate protein intake supports better outcomes.
- 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 5+1 diet safe according to NHS guidance?
The 5+1 approach can be safe for most adults, but the restricted days involve very low calorie intake (500–800 kcal), which the NHS recommends only under medical supervision. Speak to your GP before starting, especially if you have existing health conditions, take medications, or have a history of disordered eating. Individual assessment is essential.
How much weight can you lose on the 5+1 diet?
Results vary significantly between individuals. Creating a weekly calorie deficit through 5+1 typically results in loss of 0.5–1 kg per week, which aligns with NHS recommendations for sustainable weight loss. However, factors like metabolism, genetics, sleep, and activity level all affect outcomes. Track progress using MyWeightCheck's free tools for personalised insight.
How does 5+1 compare to other weight loss approaches?
The 5+1 method is a form of intermittent calorie restriction. NHS evidence suggests it works as well as traditional daily calorie restriction for weight loss, with potential adherence benefits for some people. The key factor is whether you can sustain it long-term alongside healthy eating and physical activity — that determines success.
Can I follow the 5+1 diet if I'm on diabetes medication?
Very low calorie intake days may affect blood sugar control if you're on diabetes medication. Never start the 5+1 plan without consulting your GP first — medication doses may need adjustment. Your prescriber can assess whether this approach is suitable for your individual health circumstances and medication regimen.
What should I eat on normal 5+1 days?
On non-restricted days, focus on NHS-aligned healthy eating: lean proteins, whole grains, plenty of vegetables and fruit, healthy fats, and limited processed foods and sugary drinks. Portion awareness matters even on "normal" days. Aim for balanced meals rather than unrestricted eating, as this supports steady weight loss and overall health outcomes.
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.