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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Foods to Avoid When Trying to Lose Weight
When managing your weight, understanding which foods work against your goals is just as important as knowing what to eat. This guide covers the foods and drinks most likely to sabotage your weight management efforts. Whether you're using prescription weight loss medication, following NHS weight loss guidance, or simply looking to adopt healthier eating habits, avoiding certain high-calorie and nutrient-poor foods makes sustainable weight loss significantly easier. Individual responses vary, but most people find that cutting back on these categories creates a natural calorie deficit and reduces cravings.
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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.
High-Calorie and Ultra-Processed Foods to Limit
Ultra-processed foods are specifically engineered to be hyper-palatable—meaning they trigger excessive hunger signals and make portion control difficult. Foods to avoid or significantly reduce include: sugary drinks (fizzy drinks, fruit juices, energy drinks), processed snacks (crisps, biscuits, chocolate bars), takeaway meals, and convenience foods high in trans fats and added sugars.
- Sugary beverages can add 150-300 kcal per serving with minimal nutritional value
- Processed snacks often contain hidden sugars and refined carbohydrates that spike blood sugar
- Takeaway foods typically contain excessive salt, sugar, and hidden calories in sauces
- Mass-produced baked goods combine sugar, refined flour, and unhealthy fats
These foods are calorie-dense but nutrient-poor, meaning they don't support feeling full. Swapping them for whole foods—vegetables, lean proteins, whole grains, legumes—creates a natural deficit and improves overall nutrition.
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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.
Specific Food Categories and Practical Alternatives
Alcohol is particularly problematic for weight loss—it's calorie-dense (7 kcal per gram vs 4 kcal per gram for carbohydrates), suppresses satiety signals, and encourages overeating. High-sugar condiments and sauces (ketchup, mayo, salad dressings) add calories quickly without adding volume or satisfaction. Refined carbohydrates (white bread, pastries, pasta) digest rapidly and trigger hunger spikes shortly after eating.
- Replace sugary drinks with water, herbal tea, or black coffee
- Choose whole-grain bread and pasta—they support feeling fuller longer
- Use oil-based dressings sparingly, or make your own from vinegar and olive oil
- Opt for lean proteins and vegetables instead of processed meat products
Small, consistent swaps create lasting habits without requiring perfection. Use our free BMI calculator to track how these changes affect your weight and health metrics 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 main reason some foods sabotage weight loss?
Foods high in sugar and refined carbohydrates digest quickly, triggering rapid blood sugar spikes and crashes that cause hunger shortly after eating. Ultra-processed foods are also engineered to be hyper-palatable, making portion control difficult. Whole foods—vegetables, lean proteins, legumes—require more chewing and digestion, creating natural satiety and supporting a calorie deficit.
Should I completely eliminate foods I enjoy?
Complete elimination isn't necessary and often backfires—strict deprivation leads to cravings and abandonment of healthy habits. Instead, aim to significantly reduce these foods rather than eliminate them entirely. This creates sustainable long-term change. If you're using prescription weight loss medication like Mounjaro or Wegovy, reduced appetite often makes these choices easier naturally.
Does this guidance apply if I'm on weight loss medication?
Yes, dietary changes work alongside prescription weight loss treatment. Medications like GLP-1 injections may help reduce appetite and food cravings, but they work best when combined with healthier food choices. Your GP or prescriber can give personal advice on dietary support for your specific situation.
How do I know if I'm eating the right calorie amount for weight loss?
The NHS recommends a calorie deficit of approximately 500 kcal per day for sustainable loss of around 0.5kg per week. Our GLP-1 weight loss calculator can help estimate potential weight loss and show how dietary changes support your goals. Your GP can also refer you to a dietitian for personalised guidance.
Are there foods I can eat without restriction?
Non-starchy vegetables—broccoli, spinach, peppers, courgettes—are extremely low in calories and high in fibre, so they can be eaten generously. Lean proteins (chicken breast, fish, lentils) and whole grains in reasonable portions also support weight loss. Eggs, plain Greek yoghurt, and legumes are nutrient-dense foods that support satiety.
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.