Effect of long‐term high‐fat diet feeding and fasting on energy metabolic substrates utilization in resting rats

Abstract

The effects of a high‐fat diet and fasting on resting energy expenditure and energy substrate utilization were examined using the calorimetry method. Eight 4‐week old rats were used for the high‐fat diet experiment. As a result of 5 weeks of control diet and high‐fat diet feeding, body weight of the high‐fat diet group tended to increase more than that in the control diet fed group, but the difference was not significant. The 24 hr respiratory exchange ratio was lower in high‐fat diet group. The control group showed significantly more carbohydrate oxidation than that of the high‐fat diet fed group. A fasting experiment was conducted using six 7‐ week old male rats. Resting metabolism rate was measured prior to fasting, and a fasting condition began from the next day for 3 days to energy metabolism. Both body weight and 24‐hour oxygen uptake decreased significantly as a result of 3‐days fasting. Total oxygen uptake in the first day decreased, and declined significantly on day 3 of fsting. The mean 24‐hour respiratory exchange ratio decreased significantly. Additionally, energy expenditure during the dark period, which is the active period for rats, decreased significantly with fasting, whereas energy expenditure during the light period did not increase by fasting. This study was supported by a Korean Research Foundation Grant funded by the Korean Government (MOEHRD) (KRF‐2009‐042‐G00058).