Non-exercise activity thermogenesis (NEAT): Environment and Biology

Non-exercise activity termogenesis (NEAT) is the energy expended for everything that is not sleeping, eating or sports-like exercise. It rages from the energy expended walking to work, typing, performing yard work, undertaking agricultural tasks and fidgeting.

NEAT can be measured by one of tow approaches. First, is to measure or estimate total NEAT. Here, total daily energy expenditure is measured and from it, ‘Basal Metabolic Rate-plus-thermic effect of food’ is substracted. Second is the factorial approach whereby the components of NEAT are quantified and total NEAT calculated by summing these components.

The amount of NEAT that humans perform represents the product of the amount & types of physical activities and the thermogenic cost of each activity. The factors that impact a human’s NEAT are readily divisible into environmental factors such as occupation or dwelling within a “concrete jungle” or biological factors such as weight, gender and body composition. The combined impact of these factors explains the substantial variance in human NEAT.

The variability in NEAT might be viewed as random but human and animal data contradict this. 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 mechanic studies that delineate how NEAT is regulated by neural, peripheral and humoral factors. A scheme is described where NEAT corresponds to a carefully regulated “task” of physical activity that is a crucial for weight control.