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
Where Is Weight Loss First on Your Body?
When you lose weight, your body doesn't shed fat evenly from everywhere at once. The pattern of weight loss varies significantly between individuals and depends on genetics, hormones, age, and the type of weight management approach you're using — whether through dietary changes, increased physical activity, or prescription weight loss medication like GLP-1 injections. Understanding where weight loss typically appears first can help you stay motivated and recognise progress beyond what the scales show.
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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.
How Your Body Burns Fat — The Science Behind Weight Loss
Fat loss follows a pattern controlled by your genetics and hormones rather than by your intentions. Your body tends to lose weight from areas where it was gained last and accumulated most recently. This means if you gained weight gradually over time, you'll typically lose it in reverse order — though this varies significantly between people.
Where weight loss often appears first:
- Face and neck — many people notice this early, particularly around the jawline
- Upper body — chest, shoulders, and upper back often show definition first
- Arms — reduced puffiness and improved muscle definition
- Stomach — typically one of the last places to lose fat significantly
- Thighs and legs — often the last areas to show noticeable change
Women and men experience different patterns. Men often lose abdominal fat first, whilst women may lose weight more evenly across the body or first notice it in the face, breasts, and upper body. These patterns are influenced by oestrogen and testosterone levels.
Clinically BackedWeight Loss
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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.
What Affects Where You Lose Weight First
Several factors influence your individual weight loss pattern:
- Genetics — your family's fat distribution pattern largely determines yours
- Age — younger people often lose weight more evenly; older adults may notice face and neck changes first
- Hormones — oestrogen, testosterone, and cortisol affect where fat accumulates and is lost
- Exercise type — targeted exercises don't reduce fat in specific areas, but overall fitness improves body composition
- Weight loss speed — gradual weight management may show more obvious early changes; gradual loss appears more subtle initially
If you're using GLP-1 weight management medication like Wegovy or Mounjaro, weight loss patterns follow the same genetic rules — the medication helps create the calorie deficit, but your body still chooses where to lose fat first. Track progress using our free BMI calculator and weight converter to monitor changes in your health metrics as your weight changes.
- 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.
Why do I lose weight from my face first?
The face has relatively less dense fat tissue and good blood circulation, so fat mobilisation from facial areas can be noticeable early. Additionally, even small amounts of weight loss (2–3 kg) create visible facial changes because there's less space for soft tissue. However, not everyone experiences this — it depends on your genetics and where you naturally carry weight.
Is it normal to lose weight from everywhere except my stomach?
Yes, this is very common, particularly in men. Abdominal fat (visceral fat) is often the last to go because of how your body mobilises fat stores — it prioritises mobilising fat from areas gained most recently first. Sustainable weight loss and increased physical activity, particularly strength training, can help improve abdominal composition over time.
Can I target fat loss from specific body areas?
No — spot reduction isn't possible. Your body loses fat based on genetics and hormones, not exercise location. Doing stomach crunches won't reduce belly fat specifically. However, overall weight loss combined with strength training improves muscle tone and body composition in all areas, including the areas you're concerned about.
How long does it take to notice weight loss in my face?
Many people notice facial changes within 2–4 weeks of consistent weight loss, particularly if they're losing 0.5–1 kg per week (the NHS-recommended safe rate). Others may take 4–8 weeks. It depends on your starting weight, genetics, and how much weight you lose. Using our progress tracker helps you document these changes.
Does using weight loss injections like Wegovy change where weight loss appears first?
No — Wegovy (semaglutide) and other GLP-1 medications help create a calorie deficit and reduce appetite, but your body's fat loss pattern remains genetically determined. You'll still lose weight in the same order you would with diet and exercise alone. Results vary between individuals based on their unique metabolism and genetics.
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.