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Does Non-Exercise Activity Thermogenesis Contribute to Non-Shivering Thermogenesis?
Ann M Harris1, Leslie R Macbride, Randal C Foster
1Endocrine Research Unit, Mayo Clinic, Rochester, Minnesota, 55905.
Journal of Thermal Biology
|April 4, 2007
Summary
Environmental cooling increases energy expenditure (EE) in lean males, but not through spontaneous physical activity. This study found no significant difference in physical activity levels during thermoneutral, cool, or warm conditions, indicating other mechanisms drive the EE increase.
Area of Science:
- Physiology
- Metabolism
- Environmental Health
Background:
- Non-shivering thermogenesis is a key metabolic process for maintaining body temperature.
- The role of spontaneous physical activity in energy expenditure during environmental temperature changes requires further investigation.
Purpose of the Study:
- To investigate whether spontaneous physical activity contributes to non-shivering thermogenesis in lean, healthy males.
- To quantify the effect of environmental temperature fluctuations on energy expenditure and physical activity.
Main Methods:
- Ten lean, healthy male subjects participated in the study.
- A physical activity micro-measurement system was used to monitor activity levels.
- Room temperature was systematically altered between thermoneutral (72°F), cool (62°F), and warm (82°F) conditions at two-hourly intervals.
Main Results:
- No significant differences in physical activity were observed across thermoneutral, cooling, and warming periods.
- Environmental cooling significantly increased energy expenditure (EE) by 2061 ± 344 kcal/day above basal and thermoneutral levels (p < 0.01).
Conclusions:
- The observed increase in energy expenditure during short-term environmental cooling in lean, healthy males is not attributable to increased spontaneous physical activity or fidgeting.
- Non-shivering thermogenesis likely involves metabolic pathways independent of voluntary physical movement.
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