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
How To Determine Macros For Weight Loss
Determining your macronutrient targets (protein, carbohydrates, and fats) is a practical way to structure your diet for weight loss. Rather than counting every calorie, macro-based eating helps you understand the breakdown of what you're consuming and can support sustainable weight loss when combined with a calorie deficit. This guide explains how to calculate your personal macro targets and how they fit into broader weight management in the UK.
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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.
Macronutrient Basics And Calorie Deficit
Weight loss fundamentally depends on consuming fewer calories than you burn — a calorie deficit. Macronutrients are the three nutrients that provide calories: protein, carbohydrates, and fat. Each gram of protein and carbohydrate contains 4 calories, while each gram of fat contains 9 calories. To lose weight at a healthy rate (approximately 0.5–1 kg per week, as recommended by the NHS), you typically need a deficit of around 500 calories per day. Rather than simply eating less, tracking macros ensures you're maintaining adequate protein (which preserves muscle during weight loss), while adjusting carbs and fats to fit your calorie target. This balanced approach supports better energy levels, satiety, and long-term adherence compared to very restrictive dieting.
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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.
Calculating Your Personal Macro Targets
Start by calculating your Total Daily Energy Expenditure (TDEE) — the calories your body burns at rest plus activity. Online calculators can estimate this based on your age, sex, height, weight, and activity level. Once you know your TDEE, subtract 500 calories to create a deficit. From this target calorie intake, allocate macros: aim for 1.6–2.2 grams of protein per kg of body weight (to preserve muscle), then divide remaining calories between carbs and fats based on personal preference. For example, at a 2,000 calorie target: 150g protein (600 calories), 200g carbs (800 calories), 56g fat (500 calories). Use our free BMI calculator and weight converter to track how your macros align with your healthy weight range, and monitor progress with our free progress tracker as you adjust intake over time.
- 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 split for weight loss?
There's no single "best" split — individual preference matters. Common approaches: 30–40% protein, 30–40% carbs, 20–30% fat. Higher protein (above 2g per kg body weight) supports muscle retention during calorie deficit. Choose a split you can sustain long-term rather than chasing an extreme ratio.
Do I need to count macros to lose weight?
No. Macro tracking is one tool among many. Some people lose weight successfully with simple calorie counting, intuitive eating, or structured meal plans. If macros help you stay within a calorie deficit consistently, they're useful; if they feel restrictive or triggering, other methods work just as well.
How do macros interact with weight loss medications?
Medications like GLP-1 injections (Mounjaro, Wegovy) work alongside dietary changes, not instead of them. Macro tracking can help you meet nutritional needs while eating smaller portions — a common effect of these medications. Your prescriber or a dietitian can advise on adjusting macros if appetite changes significantly.
Does macro ratio matter more than calorie deficit?
Calorie deficit is the primary driver of weight loss. Macro ratio matters secondarily — mainly for preserving muscle mass, managing hunger, and supporting exercise performance. You can lose weight on any macro split if you maintain a calorie deficit, but protein intake becomes especially important during weight loss.
How often should I adjust my macros?
Reassess every 2–4 weeks if progress stalls. As you lose weight, your TDEE decreases, so your calorie target may need adjustment (roughly 10 calories less per pound lost). Track weight and energy levels; adjust carbs or fats first while keeping protein stable.
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.