Health & safety

Last updated 1 October 2026

Out Calories gives estimates, not medical advice. It is not a medical device and does not diagnose or treat anything. When in doubt, ask a doctor or a registered dietitian.

Talk to a doctor first if you

have type 1 diabetes, or take insulin, sulfonylureas or SGLT2 inhibitors (risk of low blood sugar or ketoacidosis when fasting);
take blood-pressure medicines (diuretics) or lithium;
are pregnant, breastfeeding, or under 18;
are underweight, or have ever had an eating disorder;
have gout, kidney disease, a heart rhythm problem, or are frail.

Eating disorders

If tracking food or weight makes you anxious, guilty or preoccupied, please stop and talk to someone. Counting can help some people and harm others. In many countries there are free, confidential helplines for eating disorders; your doctor can point you to one near you.

Safe paces

The app offers goal paces from 0.25% to 1% of body weight per week. Around 0.5–1% a week is a common evidence-based range for losing fat while keeping muscle; slower is easier to sustain. Don't eat below what a professional considers safe for you, and keep protein adequate.

Fasting

Short daily fasts (12–16 hours) are well tolerated by most healthy adults.
Over 24 hours: drink water and keep up salt — fasting makes the kidneys release sodium — and consider potassium and magnesium.
Stop if you feel faint, have palpitations or feel confused.
Over 72 hours: only with medical supervision, and break the fast carefully (refeeding risk).

The fasting timeline shows typical findings from research, labelled by how strong the evidence is. Timings vary between people and depend on the last meal. Autophagy ("cell recycling") has been shown in animal studies; when or whether it happens in humans is not established.

About the numbers

Calories burned are estimated with published methods — Mifflin-St Jeor for resting energy (within ±10% for most adults), the FAO/WHO factorial method for daily activity, the ACSM walking equation, and the 2024 Compendium of Physical Activities — then corrected from your own weight trend. Food values come from USDA FoodData Central, Open Food Facts and the web, and portion sizes from photos are estimates. Your real numbers may differ.

Emergencies

Out Calories cannot help in an emergency. Call your local emergency number.