Your Total Daily Energy Expenditure (TDEE) is calculated using your Basal Metabolic Rate (BMR) multiplied by your activity level. Your BMR is determined utilizing the Harris Benedict formula (based on your age, gender, height, and weight) and your activity level is determined based on your selection or data received from your wearable device. Sedentary = BMR x 1.2, Lightly Active = BMR x 1.375, Active = BMR x 1.55, Very Active = BMR x 1.725
Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1091498/
