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
Low GI Diet for Weight Loss — Your 12-Week Plan
A low glycaemic index (GI) diet can support sustainable weight loss when combined with a calorie deficit and regular physical activity. This 12-week plan helps stabilise blood sugar, reduce cravings, and create steady weight loss of around 0.5–1 kg per week — aligned with NHS weight loss guidance. Whether you're managing your weight independently or alongside prescription weight management in the UK, understanding low GI nutrition is key to long-term success. Use our free BMI calculator to establish your starting point and track progress over your 12 weeks.
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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.
What Is a Low GI Diet and How Does It Work?
The glycaemic index (GI) measures how quickly carbohydrate foods raise blood sugar. Low GI foods (GI below 55) digest slowly, keeping you fuller longer and preventing energy crashes that trigger cravings. A 12-week low GI weight loss plan focuses on swapping high-GI refined carbs for whole grains, legumes, and protein-rich foods.
- Low GI carbs: Porridge, brown rice, lentils, beans, sweet potatoes, whole wheat bread
- High-protein foods: Chicken, fish, Greek yoghurt, eggs, tofu
- Healthy fats: Avocado, olive oil, nuts, seeds
- Vegetables: Broccoli, spinach, peppers, carrots (most are very low GI)
Combined with a calorie deficit of approximately 500 kcal per day, a low GI approach typically supports weight loss of 0.5–1 kg weekly. This method works well for weight management in the UK because it's sustainable, doesn't require strict restriction, and aligns with NHS nutrition guidance.
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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.
Building Your 12-Week Low GI Weight Loss Plan
Weeks 1–4 (Foundation): Replace white bread, pasta, and sugary cereals with low GI alternatives. Focus on protein at each meal. Track daily intake using a food app.
Weeks 5–8 (Consolidation): Introduce intermittent fasting patterns if suitable (e.g., 16:8 eating window). Add regular walking or strength training 3–4 times weekly.
Weeks 9–12 (Optimisation): Fine-tune portion sizes based on progress. Use our free progress tracker to monitor weight changes and adjust calorie intake if needed. If weight loss stalls, consult your GP about prescription weight loss options — including GLP-1 weight loss medications available through the NHS or private prescribing in the UK.
- 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 a low GI diet work without calorie counting?
Low GI foods are naturally lower in calories and more satiating, so many people lose weight without strict counting. However, weight loss still requires a calorie deficit. Tracking portions or using a food app for at least the first 4 weeks helps ensure you're in deficit and achieving your 0.5–1 kg per week loss target.
Is a low GI diet suitable if I'm taking Wegovy or other GLP-1 medication?
Yes. Low GI foods pair exceptionally well with GLP-1 medications like Wegovy (semaglutide). Both reduce appetite and blood sugar spikes. A low GI diet minimises nausea (a common GLP-1 side effect) and supports steady weight loss. Always consult your prescriber for personalised guidance if combining dietary changes with prescription weight loss medication.
How much weight can I expect to lose in 12 weeks on a low GI diet?
Following a low GI plan with a 500 kcal daily deficit typically results in 6–12 kg weight loss over 12 weeks (0.5–1 kg per week). Individual results vary based on starting weight, metabolism, and consistency. Use our GLP-1 weight loss calculator to project outcomes if you're considering combining this approach with prescription medication.
What's the difference between a low GI diet and a low-carb diet?
A low GI diet focuses on the quality and speed of carbohydrate digestion, not carb quantity — you can eat moderate carbs if they're low GI. A low-carb diet restricts total carbohydrate intake. Both support weight loss, but low GI is often more sustainable long-term and easier to maintain as a lifestyle in the UK.
Should I see my GP before starting a 12-week low GI weight loss plan?
If you have type 2 diabetes, prediabetes, or take medications affecting blood sugar, consult your GP first. A low GI diet can improve blood sugar control, which may require medication adjustments. Your GP can also assess whether prescription weight loss medication might support your 12-week goals alongside dietary changes.
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.