The “NEAT Defect” in Human Obesity: The Role of Nonexercise Activity Thermogenesis

Date: 
12-01-2007

By the law of conservation of energy, body fat increases when energy intake is consistently
greater than energy expenditure. Excess body fat and obesity are the result of sustained positive
energy balance. James A. Levine, MD, PhD, of the Division of Endocrinology, Diabetes, Metabolism, and Nutrition at Mayo Clinic Rochester, says:“Since it is now normal to be overweight or obese
in America, the urgency to understand why humans are gaining weight has intensified. In the absence
of firm data that link increased dietary intake to obesity, the role of energy expenditure in human
energy balance has come under greater scrutiny.” There are 3 components of human daily energy
expenditure (Figure 1). Basal metabolic rate is the energy required for core body functions and is
measured at complete rest without food; it accounts for about 60% of daily energy expenditure in a sedentary person. Body size accounts for nearly all the variability in basal metabolic rate—
the bigger a person, the greater his or her basal metabolic rate. The thermic effect of food is the
energy expended in response to a meal and is associated with digestion, absorption, and fuel storage. The thermic effect of food accounts for about 10% of daily energy needs and does not vary greatly from person to person. Activity thermogenesis can be subdivided into exercise activity thermogenesis and nonexercise activity thermogenesis (NEAT).

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Authors: 
JA Levine