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
Can You Lose Weight Over a Weekend?
Many people hope to lose weight quickly over a weekend, but realistic weight loss requires consistent effort over weeks and months rather than days. The NHS recommends losing weight at a rate of 0.5 to 1 kg per week for sustainable results. While weekend dietary changes might reduce bloating or water retention temporarily, lasting weight management involves ongoing lifestyle changes. Understanding how weight loss actually works helps you set achievable goals and maintain progress. Whether you're interested in prescription weight loss medication or lifestyle approaches, the foundation is consistent behaviour change rather than rapid weekend fixes.
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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.
Why Weekend Weight Loss Doesn't Work as a structured approach
Weight loss happens when your body is in a consistent calorie deficit — meaning you consume fewer calories than you burn. A single weekend of reduced eating cannot create the sustained deficit needed for meaningful weight loss. In fact, one weekend of healthy eating followed by five days of higher intake often results in no net weight loss.
Water weight can fluctuate by 1–2 kg based on sodium intake, hydration, and hormonal factors, so any "weight loss" you see on a Monday morning is usually temporary water loss, not fat loss. Fat loss requires a deficit of approximately 3,500 calories to lose 0.5 kg — something that cannot happen in two days of eating less.
- Realistic expectation: 0.5–1 kg per week through consistent calorie deficit
- Water weight changes: 1–2 kg daily fluctuations are normal and not fat loss
- Sustainable approach: Ongoing dietary and activity changes across all seven days
For evidence-based weight management in the UK, your GP can discuss approaches including lifestyle changes, and if appropriate, prescription weight loss medication. Our free BMI calculator above can help you understand your current weight status and healthy weight range.
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.
Realistic Approaches to Weight Management
Instead of targeting "weekend weight loss", focus on consistent daily habits that create a sustainable calorie deficit. This might include reducing portion sizes, choosing lower-calorie alternatives, increasing physical activity, or both combined.
For adults in the UK with a BMI of 30 or above, or a BMI of 27–29 with weight-related health conditions, prescription weight loss medication may be available. GLP-1 weight loss injections and other medications work alongside — not instead of — dietary and lifestyle changes. Try our free GLP-1 weight loss calculator to understand potential outcomes, or use our weight converter and BMI calculator to track your progress over time. Always speak with your GP about which approach is right for your individual situation.
- 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 just over one weekend?
No, sustainable weight loss requires consistent effort over weeks and months, not days. You may see temporary water weight reduction from eating less sodium or staying hydrated, but this is not fat loss. The NHS recommends losing 0.5–1 kg per week through ongoing calorie deficit and lifestyle changes.
Why does my weight fluctuate so much on weekends?
Weight naturally changes by 1–2 kg daily based on food intake, hydration status, sodium consumption, hormones, and digestion. Weekend eating patterns can cause temporary water retention or loss, but this is not meaningful fat loss and typically reverses during the week.
What's a realistic weight loss goal?
The NHS recommends losing 0.5–1 kg (1–2 lbs) per week through a sustainable calorie deficit. This requires approximately 500 calories less per day than you burn. Faster loss is possible with medical support but increases the risk of muscle loss and nutrient deficiency.
Can weight loss medication help with consistent weight management?
Yes, prescription weight loss injections like Mounjaro and Wegovy may help support weight loss when combined with dietary changes and increased physical activity. These medications require a prescription and clinical assessment from your GP or a licensed prescriber. Results vary between individuals.
How do I track my weight loss progress accurately?
Weigh yourself once weekly at the same time of day (usually Monday morning) rather than daily, as normal fluctuations can be discouraging. Use our free progress tracker to log your weight over weeks and months, which reveals true trends beyond daily water weight changes. Track measurements and how clothes fit too, as these can indicate progress even if weight fluctuates.
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.