Thermogenic Response to Fasting and Exercise in Different Aged Rats

Kwak, Ae Jung; Choi, Kwang Hae; Park, Yong Hun; Kim, Yong Woon

Abstract

PURPOSE
Recently, there has been a marked increase in childhood obesity, and that has aroused social concern. Obesity increases several metabolic disease such as hypertension, diabetes, fatty liver, heart disease and the mortality rate. Complications of obesity are more closely related with the accumulation of visceral fat. Therefore, fundamental treatment of obesity Should be the reduction of body fat. Exercise is the best way to reduce body fat, especially to consume the free fatty acid released from adipocytes. However, it is anticipated that children's response to exercise could differ from adult's. This research was done to find the difference adaptations of energy metabolisms in exercises between children and adults.
METHODS
Sprague-Dawley male rats were divided into a young group(two-three months old), adult group(six months old) and an old group(fifteen months old). At fed ad libitum, O2 consumption and CO2 production were measured before and after the exercise. Before and after fasting for 24 hours, O2 consumption and CO2 production were measured. After fasting for 24 hours, the blood was taken to analyse the plasma glucose and free fatty acid.
RESULTS
The fasting oxygen consumption decreased only in young rats compared with that of the fed state. The fasting respiratory quotient was decreased in the young and adult rats compared with those of the fed state. The post exercise oxygen consumption was increased in the young and adult rats but not in the old rats. The post-exercise respiratory quotient was decreased only in the young rats. There was no significant change of plasma glucose and free fatty acid between fed and fasting state in the young rats, while the fasting glucose levels were increased in the adult and old rats.
CONCLUSION
These results mean that the responses to fasting and exercise differ among rats of different age groups and young rats can burn fat more easily during exercise and fasting than those of the adult and old rats because of the better metabolic flexibility of young rats.