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
One Week Diet Plan for Weight Loss
A one-week diet plan can be a useful starting point for weight loss, but sustainable results require longer-term lifestyle changes. The NHS recommends losing weight at a steady rate of 0.5 to 1 kg per week through a combination of reduced calorie intake and increased physical activity. This guide covers practical strategies for a week of healthy eating, realistic expectations, and how different approaches—from dietary changes to weight loss medication—fit into a broader weight management plan in the UK.
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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.
How to Structure a One-Week Diet Plan
A successful one-week diet plan focuses on creating a moderate calorie deficit rather than extreme restriction. Aim for a daily deficit of around 500 kcal to lose approximately 0.5 kg during the week. Start by calculating your daily calorie needs using your age, sex, activity level, and current weight—your GP can help with this or you can use online NHS resources.
- Eat whole foods: vegetables, lean proteins (chicken, fish, beans), whole grains, and healthy fats
- Reduce processed foods: limit sugary drinks, biscuits, and takeaways
- Control portions: use smaller plates and measure portions until you build awareness
- Stay hydrated: drink water throughout the day rather than calorie-containing drinks
- Plan meals ahead: preparation prevents impulsive unhealthy choices
One week alone won't produce dramatic results, but it establishes patterns you can maintain. Track what you eat using a food diary or app to build awareness of your intake and identify areas to adjust.
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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.
Realistic Expectations and Professional Support
Losing 0.5 to 1 kg in one week is realistic if you maintain a consistent calorie deficit. However, initial weight loss often includes water loss, so don't expect all of it to be fat. To assess whether your weight is healthy for your height, calculate your BMI using our free BMI calculator—this gives you a baseline and helps track progress over weeks and months rather than days.
For longer-term weight loss, consider weight management support available through the NHS, including dietary advice, behaviour change programmes, or prescription weight loss medication if clinically appropriate. Prescription weight loss options like GLP-1 medications are available through NHS specialist services or private prescribing, and work best alongside the dietary and lifestyle foundations you establish in week one. Our free progress tracker can help you log your weight weekly and spot trends.
- 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 I lose weight in just one week?
Yes, modest weight loss is possible in one week through a calorie deficit of around 500 kcal per day, typically resulting in 0.5 kg loss. However, initial loss often includes water weight. Sustainable weight loss requires consistent effort over weeks and months, not days. The NHS recommends aiming for 0.5 to 1 kg per week as a safe, maintainable rate.
What should a one-week healthy diet include?
Focus on whole foods: lean proteins (chicken, fish, beans), vegetables, whole grains, and healthy fats. Limit processed foods, sugary drinks, and takeaways. Drink plenty of water, control portions, and plan meals ahead. Use our free BMI calculator to check your baseline health, then track meals daily to stay aware of your intake and calorie balance.
Is a one-week diet plan sustainable long-term?
A single week establishes useful patterns but isn't sufficient for lasting weight loss. The NHS recommends combining dietary changes with regular physical activity for sustainable results. If you struggle with long-term adherence, your GP can discuss additional support including weight loss medication or referral to NHS specialist weight management services.
Should I use a very low calorie diet plan?
Very low calorie diets (under 800 kcal daily) should only be followed under medical supervision and are not recommended for self-directed use. A moderate deficit of around 500 kcal daily is safer and more sustainable. Always consult your GP before starting any restrictive diet, especially if you have existing health conditions or take medications.
Can prescription weight loss medication help after one week?
Prescription weight loss medications like GLP-1 injections may be appropriate for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. These work best alongside dietary changes and physical activity, not instead of them. Your GP or a licensed prescriber can assess suitability following a clinical assessment. Use our GLP-1 weight loss calculator to explore potential outcomes if appropriate 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.