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
Weight Loss and Quitting Cigarettes — What You Need to Know
Many people worry about gaining weight when they quit smoking — and it's a real concern backed by evidence. On average, people gain 4–5 kg in the first year after quitting, though individual results vary widely. The good news is that quitting smoking is still one of the best things you can do for your health, and weight gain can be managed through lifestyle changes, physical activity, and in some cases, prescription weight loss support. This guide explains what happens to your body when you stop smoking, why weight gain occurs, and practical strategies to manage your weight while protecting the health gains from quitting.
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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.
Why Weight Gain Happens After Quitting Smoking
When you stop smoking, several biological changes occur that can lead to weight gain. Nicotine increases metabolism — it raises your resting metabolic rate by approximately 10–15%, meaning your body burns more calories at rest when you smoke. When you quit, this metabolic boost disappears, so you naturally burn fewer calories throughout the day.
Appetite and cravings increase. Nicotine suppresses appetite, so quitting often leads to increased hunger and food cravings. Many people also experience cravings for sweet or fatty foods as the brain seeks reward signals that smoking previously provided.
Changes in taste and smell can also increase food enjoyment, making people eat more. Additionally, smoking is often a habit linked to breaks or social situations — quitting means replacing that habit with other activities, which people sometimes fill with eating or snacking. The combination of slower metabolism, increased appetite, and behavioural changes typically results in gradual weight gain over months.
Clinically BackedWeight Loss
No appointments. No waiting rooms. Just care — from a UK-regulated online pharmacy.
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.
Managing Weight While Quitting — Evidence-Based Strategies
The NHS recommends focusing on quitting smoking first, then addressing weight management separately if needed. Timing matters: attempting aggressive weight loss while quitting smoking simultaneously can increase the risk of relapsing to smoking, so most guidance suggests stabilising your quit attempt before starting formal weight loss efforts.
Practical strategies include: increasing physical activity (which both burns calories and reduces cravings), eating more protein and fibre (which increase fullness), staying hydrated, and avoiding sugary drinks and high-calorie snacks. Use our free BMI calculator to track your current weight category and set realistic targets. If you gain more than 5–10 kg after quitting and this becomes a health concern, talk to your GP about your options — they may refer you to weight management services or discuss prescription weight loss medication as part of a comprehensive approach.
- 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.
How much weight do most people gain when they quit smoking?
Research shows the average weight gain is 4–5 kg in the first year after quitting, though some people gain less and others gain more. Individual results vary based on genetics, diet, physical activity, and how much you smoked. The good news is that even with some weight gain, quitting smoking significantly improves overall health outcomes.
Does the weight gain from quitting smoking happen quickly?
Usually no — weight gain is gradual, typically occurring over several months. Most weight gain happens in the first 3–6 months. This gives you time to establish healthy habits before weight becomes a significant issue. Starting exercise and eating well while quitting can slow or minimise weight gain.
Can I use prescription weight loss medication while quitting smoking?
Yes, but timing is important. Your GP may recommend stabilising your quit attempt first (typically 3–6 months), then discussing weight management options if needed. Prescription weight loss medications like GLP-1 injections are available in the UK but require a clinical assessment. Your GP can advise on whether this is appropriate for you.
Will weight gain from quitting smoking affect my BMI?
Possibly — it depends on how much weight you gain and your starting BMI. Use our free BMI calculator to check your current BMI and monitor it over time. If your BMI moves into a higher category, talking to your GP about weight management strategies is a sensible step.
Is the health benefit of quitting smoking worth the weight gain risk?
Yes, absolutely. Quitting smoking reduces your risk of heart disease, stroke, cancer, and respiratory disease — the health benefits far outweigh the risks from modest weight gain. Even a person who gains 5 kg after quitting is healthier than someone who continues smoking. Weight can be managed through lifestyle changes; smoking damage cannot be reversed as easily.
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.