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
Why Does Stress Cause Weight Loss?
Stress can trigger significant weight loss through hormonal and psychological changes in your body. When you're under prolonged stress, your body releases the hormone cortisol, which affects appetite regulation, metabolism, and how you store fat. This guide explains the science behind stress-related weight loss, when it becomes concerning, and how to manage your weight during stressful periods — whether through lifestyle changes or prescription weight loss medication if appropriate. Understanding this connection helps you maintain better weight management and overall health.
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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 Stress Hormones Affect Your Weight
When you experience stress, your body triggers the "fight or flight" response, releasing cortisol and adrenaline. These hormones prepare you to deal with immediate danger by suppressing appetite and redirecting energy to your muscles and brain. Cortisol also increases blood sugar and promotes fat breakdown for quick energy.
However, the effect on appetite varies between individuals. Some people lose their appetite entirely during stress, eating far less than usual and losing weight rapidly. Others experience increased cortisol levels that drive cravings for high-calorie comfort foods, leading to weight gain instead.
Chronic stress keeps cortisol elevated, which can accelerate weight loss and muscle loss. Your metabolism may also shift — some research suggests prolonged stress can increase metabolic rate slightly, though this effect is modest. Additionally, stress often disrupts sleep, and poor sleep further interferes with hormones that regulate hunger and satiety, compounding weight changes.
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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.
When Stress-Related Weight Loss Becomes Concerning
Losing more than 0.5–1 kg per week due to stress is a warning sign and should be discussed with your GP. Significant, unintentional weight loss can indicate your body is under serious strain and may lead to muscle loss, weakened immunity, nutritional deficiencies, and reduced bone density.
If you're experiencing unintentional weight loss alongside stress, anxiety, or low mood, your GP can assess whether underlying conditions like depression, anxiety disorder, or thyroid problems are involved. They can also provide referral to NHS weight management services if needed, or recommend stress management support. Try using our free BMI calculator to monitor your current weight status, and consider tracking changes over time with our progress tracker to share with your healthcare provider.
- 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 stress cause sudden weight loss?
Yes. Acute stress triggers the release of cortisol and adrenaline, which suppress appetite and increase metabolic rate. Many people experience noticeable weight loss within days or weeks of a stressful event. However, if weight loss is severe or prolonged, consult your GP to rule out underlying health conditions.
Does stress-related weight loss come back after stress ends?
Often yes, but not always. Once stress levels normalise, appetite typically returns and weight may be regained. However, if stress damaged your metabolism or muscle mass, weight loss may not fully reverse. Consistent balanced nutrition and physical activity help restore healthy weight after stress resolves.
What's the difference between stress weight loss and weight loss medication?
Stress-related weight loss is unintentional and often accompanied by poor nutrition and muscle loss. Prescription weight loss medication like GLP-1 injections works through hormone pathways to reduce appetite whilst you maintain adequate nutrition. Our GLP-1 weight loss calculator can help you understand medication-based weight loss compared to unintentional loss.
How can I manage my weight during stressful periods?
Focus on regular meals even if appetite is low, stay hydrated, maintain physical activity, and prioritise sleep. If stress is severe, speak with your GP about mental health support. They can assess whether prescription weight loss treatment or specialist support would help stabilise your weight during ongoing stress.
Should I try weight loss injections if stress is causing weight loss?
No — prescription weight loss medications are appropriate only when you're trying to intentionally lose excess weight from overweight or obesity (BMI 27+). If stress is causing unintentional weight loss, focus on stress management and nutrition first. Your GP can advise on the best approach for your situation.
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.