Does non-exercise activity thermogenesis contribute to non-shivering thermogenesis?

We wanted to examine if spontaneous physical activity contributes to non-shivering thermogenesis. Ten lean, healthy male subjects wore a physical activity, micro-measurement system while the room temperature was randomly altered at two hourly intervals between thermoneutral (72 °F), cool (62 °F) and warm (82 °F) temperatures. Physical activity measured during the thermoneutral, cooling and warming periods was not significantly different. Cooling increased energy expenditure above basal and thermoneutral values 2061±344 kcal/day (p<0.01). Thus, the increase in energy expenditure associated with short-term environmental cooling in lean, healthy males does not appear to be due to increased spontaneous physical activity or fidgeting.