What Fettle is — and isn't

Fettle is a wellness and nutrition-planning tool. It provides general information, calorie and macronutrient estimates, meal planning and shopping support for healthy adults.

Fettle is not a medical device and does not provide medical advice, diagnosis or treatment. Nothing in the app, on this website, or in our calculators replaces the advice of a doctor, pharmacist, dietitian or other qualified healthcare professional.

Estimates, not measurements

Calorie, macro, BMI and TDEE figures produced by Fettle and by the free calculators on this site are estimates based on population-level formulas (such as BMI and the Mifflin-St Jeor equation). Individual requirements vary. The Adaptive Engine refines targets over time from your own trend data, but its outputs remain estimates — not clinical measurements.

Speak to a professional first if any of these apply

• You are under 18 — Fettle is designed for adults only.

• You are pregnant, breastfeeding, or planning pregnancy. Calorie restriction is generally inappropriate in these circumstances.

• You have a medical condition affected by diet — including diabetes, kidney disease, heart disease, or a thyroid condition.

• You take medication that affects weight, appetite or blood sugar — including insulin and GLP-1 receptor agonists (such as semaglutide or tirzepatide). Your prescriber should oversee any dietary change.

• You have a history of disordered eating. Structured calorie targets and tracking are not appropriate for everyone.

Eating disorders: if tracking food or weight triggers difficult feelings or behaviours, please stop and reach out for support. In the UK, Beat's helpline is 0808 801 0677 (beateatingdisorders.org.uk), or speak to your GP. Outside the UK, contact your doctor or a local eating disorder support organisation. Fettle is designed around flexibility rather than perfection, but no app is a substitute for proper support.

Weight-loss medicines (GLP-1) users

Fettle can support the nutrition side of a medically supervised weight-management programme, but it does not manage, dose or monitor medication. If you use a GLP-1 medicine, your prescriber remains responsible for your treatment — tell them about significant dietary changes, and report side effects that affect eating to them promptly.

Listen to your body

Stop and seek medical advice if you experience dizziness, fainting, unusual fatigue, disordered eating patterns, or any concerning symptoms while following a nutrition plan. Sustainable progress never requires feeling unwell.

Emergencies: this website and app are not monitored for urgent matters. If you need urgent help, call the emergency number for the country you are in — 999 in the UK, 112 across the EU, 911 in the US and Canada. For urgent but non-emergency medical advice in the UK, call NHS 111; elsewhere, contact your local health service.

Your responsibility

By using Fettle you confirm you are 18 or over and accept that you use the information provided at your own discretion. Fettle Fitness Ltd accepts no liability for decisions made solely on the basis of the app's estimates where professional advice was warranted. See our Terms & Conditions for the full position.