Glossary

Definitions of calorie tracking, dietary assessment, and nutrition science terms used across our reviews and rankings. We define terms once and link to them from every relevant article.

Basal Metabolic Rate (BMR)

BMR is the number of calories your body burns at complete rest to keep basic physiological functions running — typically 60-75% of total daily energy expenditure.

Calorie Deficit

A calorie deficit is a state of caloric intake below total daily energy expenditure (TDEE). Sustained calorie deficit is the mechanism by which weight loss occurs.

Macronutrients (Macros)

Macronutrients (macros) are the three energy-yielding nutrient classes — protein, carbohydrate, and fat — that make up total caloric intake.

Mean Absolute Percentage Error (MAPE)

MAPE is the standard metric for measuring how far an app's predicted calorie value diverges from a known reference value, expressed as a percentage.

Net Carbs (Net Carbs)

Net carbs are total carbohydrates minus fiber (and sometimes sugar alcohols) — the carbohydrate value relevant for keto, low-carb, and diabetic management.

Total Daily Energy Expenditure (TDEE)

TDEE is the total number of calories your body burns in a 24-hour period, including resting metabolism, the thermic effect of food, and physical activity. It is the target calorie tracking apps aim to estimate.

USDA FoodData Central

USDA FoodData Central (FDC) is the US Department of Agriculture's public nutrient composition database. It is the reference source for high-trust food data and underlies most verified-tier calorie tracker databases.

Weighed Reference Meals

Weighed reference meals are calibrated test meals where every ingredient is weighed and the total kcal is computed from a high-trust composition database. They are the reference standard for calorie tracking app accuracy testing.