UBC Theses and Dissertations
The effect of exercise during pregnancy and lactation on maternal food intake, body weight and body composition, and on lactation performance in rats Courant, Geneviève Thérèse
During pregnancy, body fat stores increase in part to subsidize the high energy cost of lactation. One effect of exercise, on the other hand, is to lower percent body fat. The effect of exercise during pregnancy and lactation on body fat, and on body composition in general, is not well documented. There is also a paucity of data on the effect of exercise during these physiological states on food intake and body weight. If exercise during pregnancy decreases body fat stores, would lactation performance subsequently be compromised? This study was designed to determine the effect of moderately strenuous aerobic exercise, during rat pregnancy and lactation, on food intake, body weight, body composition and lactation performance. Virgin female Sprague-Dawley rats were divided into exercised (n=40) and sedentary (n=40) groups. Exercising rats were trained over three weeks to run on a treadmill at 30 m/min, 2 hours/day, 5 days/week. Within each group, two subgroups were then mated and three subgroups remained as virgin age controls (n=8 per subgroup). Of the mated subgroups, one was terminated within 24 hours of parturition and the other on day 14 of lactation. Subgroups of virgin sedentary and exercising controls were terminated at times corresponding to each of mating, parturition and day 14 of lactation of mated animals. Carcasses were assayed for fat, water, ash and protein. Ad libitum food intake and body weight were monitored throughout the study, as was the weight gain of pups of lactating dams. MANOVA showed the effect of activity to be significant on food intake at week three of training and during the pregnancy period (p<0.00l) and at week one (p<0.0l) and two (p<0.05) of lactation. The effect of activity was highly significant (p<0.00l) on body weight from week three of training and throughout the pregnancy and lactation periods, as well as on the percent fat, water and ash of the rat carcasses. Post hoc multimean comparisons (Scheffe) at the p<0.05 level revealed that exercise resulted in a significant increase in the food intake of virgin rats, and nonsignificant increases in the food intake of pregnant and lactating rats. Body weights of virgin, pregnant and lactating exercising rats were significantly greater than their respective sedentary controls. Despite their heavier body weights and greater food intake, the estimated carcass energy content of exercising animals was lower than that of sedentary animals. This finding was reflected in the carcass composition whereby exercising rats, whether virgin, pregnant or lactating, contained consistently less fat and more water than sedentary controls. At parturition, pregnant animals contained significantly less fat, more water and more ash than sedentary pregnant controls. After 14 days of lactation, there were no significant differences in carcass composition between exercising and sedentary dams. However, lactating rats, whether exercising or sedentary, catabolized approximately 50 percent of the body fat present at parturition. Pup weight gains were not significantly different between exercising and sedentary dams. From these findings it was concluded that the effect of exercise during pregnancy and lactation on food intake, body weight and body composition was comparable to its effect in non-gravid rats. Moderately strenuous exercise during pregnancy prevented the increase in body fat deposition normally present at this time. Despite these depleted fat stores, the energy supplied by the mobilization of the remaining fat and the increase in food intake was adequate to support normal pup growth.
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