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
Best Diet for Weight Loss in the UK
There's no single "best" diet for weight loss — what works depends on your individual circumstances, preferences, and health. However, the NHS recommends creating a sustainable calorie deficit of around 500 kcal per day, typically resulting in a loss of 0.5 to 1 kg per week. Research shows that successful weight management combines consistent dietary changes with increased physical activity. Many UK adults also find that combining lifestyle changes with prescription weight management support — where eligible — can improve outcomes.
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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.
Evidence-Based Dietary Approaches for Weight Loss
Several dietary approaches have strong evidence supporting weight loss when combined with physical activity:
- Calorie deficit dieting: Creating a 500 kcal daily deficit is the NHS-recommended baseline. Use our free BMI calculator and weight converter to track your starting point and set realistic targets based on your healthy weight range.
- Mediterranean diet: Strong evidence for cardiovascular health and sustainable weight loss. Emphasises vegetables, whole grains, fish, and olive oil.
- Low-carbohydrate approaches: Effective short-term, though long-term outcomes are similar to standard calorie restriction when total calories are matched.
- Intermittent fasting (5:2 or 16:8): Some people find this helps create a calorie deficit more easily, though results vary significantly between individuals.
The most important factor is choosing an approach you can sustain long-term. NHS weight management guidance emphasises that gradual weight management (more than 1.5 kg per week) increases the risk of muscle loss and is not recommended without medical supervision.
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.
Adding Professional Support and Prescription Options
If you've tried dietary changes without sustained results, prescription weight loss support may be an option. In the UK, GLP-1 weight loss injections such as Mounjaro and Wegovy are available for adults with a BMI of 30 or above, or 27 or above with weight-related health conditions. These are prescription-only medications that work alongside — not instead of — improved diet and physical activity.
Our GLP-1 weight loss calculator can help you estimate potential outcomes at different doses. Access via the NHS requires referral to specialist weight management services, or through private prescribing services following a clinical assessment. Remember that individual results vary significantly, and any prescription medication requires ongoing review by a healthcare professional.
- 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 is the best diet to lose weight fast in the UK?
The NHS recommends losing 0.5–1 kg per week for sustainable results. Very gradual weight management increases muscle loss and is not recommended without medical supervision. Crash dieting typically leads to rebound weight gain. Focus on a sustainable 500 kcal daily deficit through reduced calories and increased activity.
Is calorie counting the best way to lose weight?
Calorie deficit is scientifically proven and essential for weight loss. However, different people find different tracking methods work best — some count calories directly, others use portion control or meal planning. The "best" approach is the one you'll maintain consistently long-term.
Which diet is recommended by the NHS for weight loss?
The NHS doesn't prescribe one specific diet. Instead, it recommends creating a sustainable calorie deficit (roughly 500 kcal/day) through balanced eating and activity. The NHS Weight Loss Plan offers a free digital programme. For BMI above 30 with comorbidities, specialist weight management services may include prescription support.
Can weight loss injections replace diet changes?
No. Prescription weight loss medications like Mounjaro and Wegovy are prescribed alongside — not instead of — dietary changes and physical activity. Clinical trials show they're most effective when combined with lifestyle modifications. They support appetite regulation and fullness, making calorie reduction easier for many people.
How do I know what weight loss approach is right for me?
Start by assessing your current BMI and health using our free BMI calculator. Then consider your preferences — do you prefer tracking, portion control, or specific foods? Consult your GP for personalised advice, especially if you have health conditions. Many people benefit from a NHS tier 1 or 2 weight management programme before specialist support.
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.