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
What Role Do Macros Play in Weight Loss?
Macronutrients (protein, carbohydrates, and fats) are the three nutrients your body uses for energy and function. While total calorie intake is the primary driver of weight loss, the balance of macros you consume can affect hunger, muscle preservation, energy levels, and how sustainable your weight management uk approach is. Understanding macros helps you make better food choices alongside any weight loss strategy.
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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 Do Macronutrients Affect Weight Loss?
All three macronutrients provide energy, but they have different effects on your body. Protein has the highest thermic effect, meaning your body burns more calories digesting it — it also supports muscle maintenance during weight loss and helps you feel fuller longer. Carbohydrates provide energy for exercise and daily activity, but quality matters; whole grains and vegetables are more satiating than refined options. Fats are calorie-dense (9 kcal per gram vs 4 for protein and carbs) but essential for hormone function and nutrient absorption.
- A higher protein intake (1.6–2.2g per kg of body weight) may help preserve muscle during weight loss
- Adequate fibre from carbohydrates supports fullness and gut health
- Healthy fats support hormone balance and nutrient absorption
- Individual macro ratios vary — there's no single "perfect" split for everyone
The most important factor remains total calorie intake: you need a deficit of approximately 500 kcal per day to lose around 0.5 kg per week, in line with NHS weight loss 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.
Macros and Prescription Weight Loss Medication
If you're using GLP-1 weight loss medication (such as Wegovy, Mounjaro, or other prescription weight loss uk options), macro balance becomes even more relevant. These medications reduce appetite and slow stomach emptying, which can make eating adequate protein challenging when intake is naturally lower. Prioritising protein-rich foods helps preserve muscle mass while losing fat.
You can use our GLP-1 weight loss calculator to explore potential outcomes with medication. Regardless of whether you're using medication or pursuing lifestyle-based weight loss, most evidence suggests that sustainable approaches combine appropriate calorie intake, adequate protein, whole food choices, and regular physical activity. Your GP can provide personalised weight loss medication nhs guidance if you meet eligibility criteria.
Practical macro strategies for weight loss include: tracking intake initially to understand portion sizes, prioritising lean protein at each meal, choosing whole grains over refined carbs, including healthy fats (nuts, avocado, olive oil), and eating plenty of vegetables for volume and fibre without excess calories. Consider using our BMI calculator and progress tracker to monitor your bmi weight loss changes over time. Remember that macro ratios matter less than overall calorie deficit — work with a pattern that feels sustainable for you.
- 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's the best macro ratio for weight loss?
There's no single "best" ratio — it depends on your preferences and lifestyle. Common approaches include 30–40% protein, 30–40% carbs, 20–30% fat. Higher protein (35–40%) may help with satiety and muscle preservation. The most important factor is maintaining a calorie deficit of around 500 kcal/day for ~0.5 kg/week loss, as recommended by the NHS.
Do I need to count macros to lose weight?
No. Many people lose weight successfully without tracking macros, focusing instead on total calorie intake and food quality. Macro tracking is a tool that helps some people stay accountable and ensure adequate protein. Start simple — focus on calorie deficit first, then refine macro balance if needed.
How does protein help with weight loss?
Protein increases satiety (helps you feel fuller), has a higher thermic effect (your body burns more calories digesting it), and preserves muscle mass during weight loss. Aim for 1.6–2.2g per kg of body weight daily. Good sources include chicken, fish, eggs, Greek yoghurt, legumes, and tofu.
Can prescription weight loss injections affect my macro needs?
Yes. GLP-1 medications like Wegovy reduce appetite, so your total intake naturally drops. Prioritising protein-rich, nutrient-dense foods becomes especially important to preserve muscle and stay nourished on a smaller intake. Your prescriber can advise on nutrition alongside medication.
What's the relationship between macros and the NHS weight loss plan?
The NHS Weight Loss Plan emphasises balanced nutrition, portion control, and calorie awareness rather than strict macro ratios. Macros support this by helping you make nourishing choices within your calorie target. Focus on whole foods, adequate protein, and regular activity for best results.
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.