Evidence-based explanations of body mass index, metabolic rates, daily energy expenditure, and fitness metrics.
Body Mass Index (BMI) is a simple ratio of weight to height, used as a population-level screening tool to flag whether someone's weight may fall into a range associated with higher health risk. It does not measure body fat directly, and it is not a diagnosis — it's a starting point that's often followed up with other measurements or a conversation with a healthcare provider.
BMR (Basal Metabolic Rate) is the estimated number of calories your body burns at complete rest just to keep basic functions running. TDEE (Total Daily Energy Expenditure) is BMR plus the calories burned from daily activity and exercise. TDEE is always higher than BMR for anyone who moves at all during the day, and TDEE — not BMR — is the number typically used to plan calorie intake for maintaining, losing, or gaining weight.