Physical Activity Energy Expenditure Assessment

Physical activity energy expenditure (PAEE) represents the energy cost of bodily movements beyond resting metabolic needs and diet‐induced thermogenesis. It is a key component of total energy expenditure (TEE), reflecting the caloric demand of daily life and structured exercise. Accurate quantification of PAEE underpins research into obesity, cardiometabolic health, and the design of public health guidelines. Traditional gold‐standard methods employ doubly labelled water (DLW) to determine TEE, from which PAEE is derived by subtracting resting energy expenditure (REE) and the thermic effect of food. However, DLW is costly and impractical for large studies. As a result, alternative approaches have emerged, combining wearable sensors (accelerometers, heart‐rate monitors, respiration belts) with predictive algorithms. Calibration protocols, machine‐learning models and multi‐sensor fusion have enhanced precision in free‐living settings, enabling population‐level surveillance and individual feedback. Current efforts focus on device calibration across populations, integration of physiological signals, and validation against criterion methods to support personalised health monitoring and epidemiological research.

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Physical Activity Energy Expenditure Assessment publication trend

The graph below shows the total number of articles in physical activity energy expenditure assessment across all publications each year (not limited to Nature Index journals).

Technical terms

Physical Activity Energy Expenditure (PAEE): The component of total energy expenditure attributable to all bodily movements above resting levels, expressed in kilojoules or kilocalories per kilogram per day.

Total Energy Expenditure (TEE): The sum of resting energy expenditure, diet‐induced thermogenesis and physical activity energy expenditure over a given period.

Metabolic Equivalent of Task (MET): A unit representing the ratio of the rate of energy expended during an activity to the resting metabolic rate; 1 MET is defined as 3.5 mL O₂ kg⁻¹ min⁻¹.

Accelerometry: A method of estimating physical activity by measuring acceleration forces, typically via triaxial sensors, to infer intensity and duration of movement.

Doubly Labelled Water (DLW): A reference technique for measuring free‐living total energy expenditure by tracking the differential elimination of stable isotopes of hydrogen and oxygen in body water.

References

1. Device-measured physical activity and type 2 diabetes mellitus risk. Frontiers in Endocrinology (2023).
2. Estimating energy expenditure from wrist and thigh accelerometry in free-living adults: a doubly labelled water study. International Journal of Obesity (2019).
3. Fusion of Heart Rate, Respiration and Motion Measurements from a Wearable Sensor System to Enhance Energy Expenditure Estimation. Sensors (2018).