Non-exercise activity thermogenesis


Non-exercise activity thermogenesis (NEAT) is the energy expended that is not from sleeping,
eating or sports-like exercise. It ranges from the energy expended walking to work, typing,
performing yard work, undertaking agricultural tasks and fidgeting. NEAT can be measured by
one of two approaches. The first approach is to measure or estimate total NEAT. Here, total daily
energy expenditure is measured and from it is subtracted BMR + thermic effect of food. The
second is the factoral approach whereby the components of NEAT are quantified and total NEAT
calculated by summing these components. The amount of NEAT that human subjects perform
represents the product of the amount and types of physical activities and the thermogenic cost of
each activity. The factors that affect the NEAT of a human subject are readily divisible into
biological factors, such as weight, gender and body composition, and environmental factors, such
as occupation or dwelling within a ‘concrete jungle’. The combined impact of these factors
explains the substantial variance in human NEAT. The variability in NEAT might be viewed as
random but human data contradict this perception. It appears that changes in NEAT subtly
accompany experimentally-induced changes in energy balance and are important in the
physiology of weight change. NEAT and sedentariness may thus be important in obesity. It then
becomes intriguing to dissect mechanistic studies that delineate how NEAT is regulated by neural,
peripheral and humoral factors. NEAT may be a carefully-regulated ‘tank’ of physical activity that
is crucial for weight control.

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James A. Levine