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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Plant-Based Supplements for Weight Loss — What the Evidence Shows
Plant-based supplements are widely marketed for weight loss, but evidence for most is limited. This guide explores what the research shows about popular natural supplements, how they compare to prescription weight loss medication, and how to approach weight management safely in the UK. While some plant-based ingredients may offer modest support, sustainable weight loss typically requires combined lifestyle changes and, in some cases, prescription treatment. Always consult your GP before starting any supplement, especially if you're taking other medications.
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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.
Common Plant-Based Weight Loss Supplements and What Research Shows
Green tea extract contains catechins that may modestly increase fat burning, but studies show minimal weight loss (typically 0.5–2 kg over several months). Garcinia cambogia (hydroxycitric acid) has mixed evidence with limited real-world weight loss benefit. Conjugated linoleic acid (CLA) from plant sources may help reduce body fat slightly but requires high doses. Glucomannan, a soluble fibre, can help you feel fuller and may support modest weight loss when combined with a reduced-calorie diet. Caffeine from natural sources (green tea, guarana, coffee) can temporarily boost metabolism and may aid fat loss by 1–3 kg over several months. Fibre supplements (psyllium, inulin) support satiety but work best alongside dietary changes. Most supplements lack the robust clinical evidence that prescription weight loss medications have. Using our free BMI calculator on this page helps you establish your baseline before considering any weight management approach.
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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.
How Plant-Based Supplements Compare to Evidence-Based Weight Loss
Plant-based supplements typically produce modest results (often 1–5 kg over 3–6 months) and work best alongside calorie reduction and exercise. In contrast, prescription weight loss medications like GLP-1 injections have strong clinical trial evidence: the STEP trial showed semaglutide (Wegovy) helped people lose around 15% of body weight on average. If you're considering weight management options, the NHS recommends starting with lifestyle changes, then consulting your GP about whether prescription medication might help. Our GLP-1 weight loss calculator can help you understand projected outcomes if prescription treatment becomes appropriate. For weight management in the UK, tier 1 approaches (self-help, calorie awareness) come first, with specialist support available if needed.
- 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.
Are plant-based weight loss supplements safe?
Most are safe for most people, but side effects are possible—glucomannan can cause bloating, and caffeine may cause jitteriness. Plant supplements are not regulated as strictly as medications. Always tell your GP about supplements you're taking, especially if you have health conditions or take other medications.
Do any plant-based supplements actually work for weight loss?
Some have modest evidence: green tea, caffeine, and glucomannan may support small weight losses (1–3 kg) alongside diet and exercise. However, none match the clinical evidence for prescription weight loss medications. Sustainable weight loss typically requires calorie deficit and lifestyle change—supplements alone rarely produce significant results.
Can I use plant-based supplements instead of prescription weight loss medication?
Plant supplements and prescription medications work very differently. If you have a BMI over 30 or 27+ with weight-related health conditions, your GP can assess whether prescription weight loss treatment is appropriate. Plant supplements may support lifestyle changes but aren't substitutes for evidence-based medication when clinically needed.
What's the most effective approach to weight loss in the UK?
The NHS recommends a combined approach: calorie deficit of 500 kcal/day, increased physical activity, and behaviour change support. For some people, prescription weight loss injections (available through NHS specialist services or private prescribing) help alongside lifestyle changes. Our free BMI calculator and weight loss calculator can help you understand your starting point and potential outcomes.
Should I try plant-based supplements before seeing my GP about weight management?
You can try lower-risk supplements (like fibre or green tea), but inform your GP about your weight management goals. Your GP can assess your individual health, check your BMI using our free calculator, and advise whether prescription support would help. Don't delay professional advice if weight is affecting your health—early intervention is often more effective.
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.