A Brief Primer on TEE, BMR, RMR, and the Thermic Effect of Food

When discussing human metabolism, four concepts often arise: total daily energy expenditure (TEE), basal metabolic rate (BMR), resting metabolic rate (RMR), and the thermic effect of food (TEF). Energy expenditure science can feel alphabet-soup–heavy, so let’s clarify these key terms in more depth:

• Total Daily Energy Expenditure (TEE): TEE is the total energy (calories) you burn in 24 hours. It encompasses every energy-demanding process in your body—from keeping your heart pumping to walking the dog. In other words, TEE is the sum of all calories you burn in a day—this includes everything from keeping your organs running (which we generally call BMR or RMR) to the energy cost of digesting your meals (the TEF) and the calories used during physical activity or exercise.

• Basal Metabolic Rate (BMR): BMR is the minimum energy your body needs to support vital functions at complete rest—heartbeat, breathing, cellular repair, brain function—in a true baseline condition. It’s measured under very controlled circumstances: after waking up from at least 8 hours of sleep, in a fasted state, lying quietly in a temperature-controlled room. Because BMR accounts for about 50–70% of TEE in a typical adult, small changes in BMR can impact overall metabolism. The gold standard for measuring BMR is indirect calorimetry, where you breathe into a device that measures oxygen intake and carbon dioxide output, which can be converted into the calories you burn at rest.

• Resting Metabolic Rate (RMR): RMR is similar to BMR but is measured under less strict conditions—perhaps you’ve had a light rest (not necessarily 8 hours of sleep) or are sitting quietly instead of lying in a bed. RMR tends to be slightly higher than BMR (~5–10%) because it may reflect minor activities like being awake and seated. Nonetheless, many studies (and clinicians) use RMR and BMR almost interchangeably to indicate baseline metabolic rate. 

• Thermic Effect of Food (TEF): Every time you eat, your body expends energy to chew, digest, absorb, transport, and store nutrients. This post-meal energy expenditure is called the thermic effect of food. TEF generally contributes about 10% of total daily energy expenditure. However, it can vary based on meal composition (protein has a higher thermic effect than fats or carbohydrates) and individual metabolic differences.