DESIGN: To characterize the dynamic changes in continuously measured resting EE, substrate utilization, and hormonal axes simultaneously in response to mild reduction in environmental temperature, we performed a cross-over intervention.

METHODS: Twenty-five volunteers underwent two 12-h recordings of EE in whole room indirect calorimeters at 24 and 19?°C with simultaneous measurement of spontaneous movements and hormonal axes.

RESULTS: Exposure to 19?°C resulted in an increase in plasma and urine norepinephrine levels (P<0.0001), and a 5.96% (P<0.001) increase in EE without significant changes in spontaneous physical activity. Exposure to the lower temperature resulted in a significant increase in free fatty acid levels (P<0.01), fasting insulin levels (P<0.05), and a marginal decrease in postprandial glucose levels. A small but significant (P<0.002) increase in serum free thyroxine and urinary free cortisol (P<0.05) was observed at 19?°C.

CONCLUSIONS: Our observations indicate that exposure to 19?°C, a mild and tolerable cold temperature, results in a predictable increase in EE driven by a sustained rise in catecholamine and the activation of counter-regulatory mechanisms.

Eur J Endocrinol. 2010 Dec;163(6):863-72. Epub 2010 Sep 8.

Celi FS, Brychta RJ, Linderman JD, Butler PW, Alberobello AT, Smith S, Courville AB, Lai EW, Costello R, Skarulis MC, Csako G, Remaley A, Pacak K, Chen KY.

Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-1613, USA. fc93a@nih.gov