The effect of prolonged physical training and high fat diet on heart size and body weight in rats.

Abstract

White male Woodlyn Wistar rats (aged 9-10 weeks) were subjected to prolonged physical training on a treadmill for 10 weeks. After 4 weeks half of the rats received a high fat test diet (45%) (Nutritional Biochemical Corporation) while the control group was fed standard lab chow (Purina lab chow). The body weights, heart weights, and heart weight per 100 g body weight were compared in a two by two factorial analysis, the independent variables being condition (exercise or sedentary) and diet (balanced or high fat). After 10 weeks the difference in body weight between the sedentary rats (body weight (BW) equals 514.4 plus or minus 76.4 g) and the exercise rats (BW equals 389 plus or minus 44 g) was significant (p less than 0.05). The difference in body weight between the high fat diet rats (BW equals 479 plus or minus 80 g, n equals 10) and the balanced diet group (BW equals 424 plus or minus 76 g, n equals 10) was also significant (p less than 0.05). No significant differences were observed in heart weight among any of the groups whereas a significant difference was noted between the sedentary group and the exercise group with respect to heart weight : body weight ratio. Thus the exercise rats had relatively larger hearts than the sedentary group (p less than 0.05) but no evidence for cardiac hypertrophy in the exercise group compared with the sedentary group ws observed. The difference with regard to heart ratios between the balanced diet and high fat diet groups was not significant and no interaction was present (p equals 0.065). It was concluded that cardiac hypertrophy is not necessarily a consequence of prolonged physical training but is a product of the type of training, the intensity and duration, and the emotional stress involved. Prolonged physical exercise was a powerful deterrent to weight gain even in rats on a high fat diet. In the absence of the development of cardiac hypertrophy in response to prolonged training, further work is needed to quantify the factors that result in cardiac hypertrophy and to identify other changes that may be occurring in the cardiovascular system in response to prolonged physical training.