When discussing energy expenditure and metabolism, most people focus on deliberate exercise. However, the movement we do in everyday life—what researchers call non-exercise activity—actually accounts for a significant portion of daily energy use.
Total Daily Energy Expenditure (TDEE)
Total daily energy expenditure consists of three main components: basal metabolic rate (BMR), the thermic effect of food (TEF), and activity energy expenditure (AEE). Activity energy expenditure includes both structured exercise and incidental movement throughout the day.
Non-Exercise Activity Thermogenesis (NEAT)
Non-exercise activity thermogenesis refers to the energy expended during daily activities that are not sleeping, eating, or deliberate exercise. This includes occupational activities, fidgeting, maintaining posture, and spontaneous movement. Research shows that NEAT can vary dramatically between individuals and can contribute significantly to total daily energy expenditure.
Components of Daily Movement
Occupational Activity: Movement and exertion during work varies greatly depending on job type. Sedentary office work requires minimal movement, while physically demanding occupations involve substantial energy expenditure.
Leisure Activity: Recreational activities, whether structured or unstructured, contribute to daily energy use. Walking, gardening, and household tasks all involve physical activity.
Spontaneous Movement: Fidgeting, postural adjustments, and unconscious movement vary between individuals and can contribute meaningfully to daily energy expenditure.
Active Transport: Walking or cycling for transportation contributes to daily activity levels. The prevalence of motorised transport has reduced this component for many people.
Individual Variation in Daily Activity
Daily movement patterns vary tremendously between individuals based on occupation, lifestyle, personal preferences, and environmental factors. Research shows that some individuals naturally engage in significantly more incidental movement than others, a trait that appears to be influenced by both genetic and environmental factors.
Effects on Energy Balance
Because NEAT and daily activity vary substantially between individuals, total daily energy expenditure differs significantly even among people of similar size and body composition. This is one reason why caloric requirements vary between individuals.
Long-Term Consistency
Research suggests that individuals tend to maintain consistent patterns of daily activity over time. Some people naturally maintain higher activity levels, while others are naturally more sedentary. These patterns can influence overall energy balance, though individual circumstance varies greatly.
Environmental and Occupational Factors
Modern lifestyle changes have reduced incidental activity for many people. Increased use of motorised transport, more sedentary work environments, and labour-saving devices have decreased average daily activity for many in developed countries. However, activity levels remain highly variable between individuals.
Context and Individual Circumstances
Daily activity is influenced by personal circumstances, work requirements, health status, age, and environmental factors. There is tremendous variation in what constitutes "typical" activity for different individuals, and changes in activity require consideration of individual circumstances.
Educational Context
This article explains the mechanisms through which daily activity contributes to energy expenditure. Understanding these processes is educational. However, how activity levels affect individuals varies based on personal circumstances and health status. Any significant changes in activity patterns should be made with consideration of individual circumstances.