Total Daily Energy Expenditure (TDEE) is the total number of calories your body burns in a day to maintain its current weight. It combines several factors: Basal Metabolic Rate (BMR), which is the energy used for basic bodily functions like breathing and circulation; energy expended through physical activity, such as exercise and daily movements; the Thermic Effect of Food (TEF), which is the energy required for digestion and nutrient absorption; and Non-Exercise Activity Thermogenesis (NEAT), which includes fidgeting or small movements. TDEE varies based on age, gender, weight, body composition, and activity level.
Calculating TDEE is crucial for setting calorie goals, whether for weight loss, muscle gain, or maintenance. For example, consuming fewer calories than your TDEE results in a caloric deficit, promoting fat loss, while eating more leads to a surplus, aiding muscle growth. Understanding your TDEE helps tailor your nutrition and fitness plans effectively, making it a cornerstone of body composition management. Tools like this online TDEE calculator or wearable devices can estimate TDEE, but these are just approximations and may require adjustment over time.
BMR Definition: Your Basal Metabolic Rate (BMR) is the number of calories you burn as your body performs basic (basal) life-sustaining function. Commonly also termed as Resting Metabolic Rate (RMR), which is the calories burned if you stayed in bed all day. In either case, many utilize the basal metabolic rate formula to calculate their body’s metabolism rate.
Your BMR defines your basal metabolism rate which makes up about 60-70% of the calories we use (“burn” or expend). This includes the energy your body uses to maintain the basic function of your living and breathing body, including:
Your unique metabolism rate, or BMR, is influenced by a number of factors including age, weight, height, gender, environmental temperature, dieting, and exercise habits.
The BMR formula above uses the Mifflin-St Jeor Equation.
Mifflin-St Jeor Equation:
where: W is body weight in kg, H is body height in cm, A is age
While the two are used interchangeably, there is a key difference in their definitions. Resting metabolic rate, or RMR for short, is the rate at which the body burns energy in a relaxed, but not fully inactive state. It is also sometimes defined as resting energy expenditure, or REE. BMR measurements must meet total physiological equilibrium while RMR conditions of measurement can be altered and defined by contextual limitations.
*All BMR calculations, even using the most precise methods through specialists, will not be perfectly accurate in their measurements. Not all human bodily functions are well understood just yet, so calculating total daily energy expenditure (TDEE) derived from BMR estimates are just that, estimates. When working towards any sort of health or fitness goal, BMR can aid in laying down the foundations, but from there on, it has little else to offer. A calculated BMR and thus TDEE may result in unsatisfactory results because of their rough estimates, but maintaining a daily journal of exercise, food consumption, etc., can help track the factors that lead to any given results and help determine what works, as well as what needs to be improved upon. Tracking progress in said journal and making adjustments over time as needed is generally the best indication of progress towards reaching personal goals.