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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Low Carb and Weight Loss: What the Evidence Shows
Low carbohydrate diets are a popular weight management approach in the UK, but how effective are they really? Research shows that low carb eating can support weight loss, particularly in the short term, when combined with other healthy habits. The evidence suggests that weight loss with low carb diets works primarily through creating a calorie deficit, rather than the carbohydrates themselves being "special". This guide explains what the science tells us about low carb diets, how they compare to other approaches, and how they fit into broader weight management strategies within the UK health system.
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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 Low Carb Diets Work for Weight Loss
Low carbohydrate diets reduce or restrict foods containing carbs — such as bread, rice, pasta, and sugar — while increasing protein and fat intake. The theory is that lower carb intake reduces insulin spikes and hunger signals, making it easier to eat fewer calories overall.
What the research shows:
- Short-term weight loss (6–12 months) on low carb diets is typically modest to moderate — around 3–6kg for many people
- Long-term results (1–2 years) are similar to traditional calorie-restricted diets — both produce weight loss primarily through calorie deficit
- Some people find low carb eating easier to stick to because protein and fat are more satiating (filling)
- Individual results vary significantly based on adherence and overall lifestyle
The NHS does not recommend one specific diet type as superior. Instead, the NHS Weight Loss Plan emphasises finding an approach you can sustain long-term, which may or may not be low carb. Using our free weight converter and BMI calculator can help you track your starting point and monitor progress objectively.
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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.
Low Carb vs Other Weight Management Approaches
Low carb diets are one of many effective weight loss approaches available. Mediterranean diet, balanced calorie restriction, intermittent fasting, and GLP-1 weight loss medications all have evidence supporting their use in weight management in the UK.
What matters most is finding a sustainable approach that fits your lifestyle and health needs. Some people succeed with low carb eating; others find a balanced moderate-carb diet more sustainable. Our GLP-1 weight loss calculator can help you compare potential outcomes if you're considering prescription weight loss medication alongside dietary changes. For personalised advice about which approach suits you best, your GP can discuss your individual health profile and recommend tier 2 or tier 3 NHS weight loss support if appropriate.
- 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 a low carb diet better for weight loss than other diets?
Not necessarily. Research shows that weight loss on low carb diets is similar to traditional calorie-restricted or Mediterranean diets over 1–2 years. The best diet is the one you can stick to long-term. Low carb may suit some people because protein and fat are filling, but results vary individually.
How quickly will I lose weight on a low carb diet?
Initial weight loss can be faster (partly water loss), but sustainable weight loss is typically 0.5–1kg per week according to NHS guidance. This applies to low carb and other approaches. Very gradual weight management is not recommended without medical supervision. Use our progress tracker to monitor realistic, sustainable progress.
Can I combine a low carb diet with GLP-1 weight loss medication?
Yes. GLP-1 medications like Mounjaro and Wegovy are designed to work alongside dietary changes and increased physical activity, not replace them. Many people use prescription weight loss medication together with low carb or balanced eating. Your prescriber will advise on the best combination for you.
Is low carb diet safe for everyone?
Low carb diets are safe for most adults but may not suit people with certain health conditions, those taking specific medications, or pregnant women. Always discuss dietary changes with your GP before starting, especially if you have type 2 diabetes or take blood sugar medications.
What counts as "low carb" in the UK?
There's no official definition, but typical low carb diets contain 20–100g carbs daily (very low) or 100–150g (moderate low carb), compared to 200–300g in a standard balanced diet. Our BMI calculator and weight converter help you understand your baseline — your GP can advise on appropriate carb targets for your individual needs.
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.