Effects of cold acclimation, cold exposure, and palatability on postprandial thermogenesis in rats

Groups of rats were maintained at 24 degrees C and 4 degrees C (WA, CA). At each temperature one group was fed a pelleted stock diet, while another was fed in addition, 3 kJ of palatable food at 1-h intervals for a total of 8 h during the day. After 2 weeks the thermogenic response to both 3 kJ and 30 kJ of palatable food was determined by measuring oxygen consumption over a period of 3 h. Food intake revealed two phases of postprandial thermogenesis. During the initial cephalic phase which lasted 30 min the O2 consumption increased by about 40 percent with both test meals and the response was comparable for WA and CA rats tested at the same temperature. During the subsequent gastrointestinal phase the response was proportional to the size of the meal and the CA rats were always more responsive than the WA rats specially when tested at 4 degrees C. The results suggest that postprandial thermogenesis during the initial cephalic phase is related to food palatability and that cold exposure and cold acclimation cause an enhanced response during the second phase of meal thermogenesis.