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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What's the Best Carb Protein Fat Ratio for Weight Loss?
The right balance of carbohydrates, protein, and fat matters when you're trying to lose weight. There's no single "perfect" ratio that works for everyone — individual needs vary based on your metabolism, activity level, and personal preferences. However, evidence-based nutrition science and NHS weight management guidance suggest certain ratios tend to support sustainable weight loss better than others. This guide explains what the research shows and how macronutrient balance fits alongside other weight loss approaches, including prescription weight loss medication like Mounjaro or Wegovy if your GP recommends it.
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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.
Understanding Macronutrient Ratios for Weight Loss
Macronutrients are carbohydrates, protein, and fat — the three main nutrients that provide energy. When managing weight, the ratio you consume can affect hunger, energy levels, and how your body uses stored fat. The NHS and most health organisations focus less on strict ratios and more on overall calorie intake and food quality, but research shows that higher protein intake (around 25–35% of daily calories) generally supports weight loss better than very low protein diets.
- Protein (25–35% of calories): Supports muscle preservation, increases satiety, and has a higher thermic effect (your body burns more calories digesting it)
- Carbohydrates (40–50% of calories): Should focus on whole grains, vegetables, and fibrous sources rather than refined carbs
- Fat (25–35% of calories): Unsaturated fats from sources like olive oil, avocados, and nuts support health and satiety
These are approximate ranges — your ideal ratio depends on your individual response. Some people lose weight more easily on lower-carb approaches, whilst others do better with moderate carbohydrate intake. The key is finding a ratio you can sustain long-term alongside a reduced-calorie diet.
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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.
Macronutrient Balance and Weight Loss Medication
If you're taking prescription weight loss medication — whether that's GLP-1 medications like Wegovy (semaglutide) or Mounjaro (tirzepatide) — macronutrient ratio becomes even more important. These medications may reduce your appetite and help you feel fuller on smaller portions, which means you're more likely to eat less overall. Maintaining adequate protein intake (around 1.2–1.6g per kg of body weight) helps protect muscle mass during weight loss, preventing the loss of lean tissue alongside fat loss.
Our free GLP-1 weight loss calculator can help you estimate potential weight loss outcomes and understand how medication fits into your overall plan. Combine this with sustainable nutrition choices — including a balanced carb, protein, and fat ratio — and you're more likely to achieve lasting results. Always work with your GP or a registered dietitian for personalised guidance on macronutrient targets suited to your health needs and weight loss goals.
- 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?
Evidence suggests around 25–35% protein, 40–50% carbs, and 25–35% fat works well for most people. However, the "best" ratio is one you can sustain long-term. Focus on calorie deficit first — macronutrient balance is secondary. Work with your GP or a registered dietitian for personalised guidance.
Does high protein help weight loss?
Yes — higher protein intake (25–35% of daily calories) increases satiety, preserves muscle during weight loss, and has a higher thermic effect (your body burns more calories digesting it). This makes it easier to stick to a reduced-calorie diet without feeling overly hungry.
Should I cut carbs to lose weight?
Not necessarily. Very low-carb diets can work short-term, but evidence shows that sustainable weight loss depends more on overall calorie deficit than carb restriction alone. NHS guidance recommends focusing on whole grains, vegetables, and fibrous carbs rather than refined carbohydrates.
How do GLP-1 injections affect my nutrition needs?
GLP-1 medications like Wegovy or Mounjaro reduce appetite and help you eat smaller portions. Maintaining adequate protein intake becomes more important to protect muscle mass. You may naturally eat less overall, so prioritise nutrient-dense foods — protein, vegetables, and healthy fats — rather than high-calorie, low-nutrition options.
How do I calculate my ideal daily protein intake?
A common recommendation is 1.2–1.6g of protein per kg of body weight. Use our free BMI calculator and weight converter to establish your baseline, then multiply your weight in kg by 1.2 to 1.6 to find your daily protein target. For personalised advice, consult your GP or a registered dietitian, especially if you're taking weight loss medication.
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.