Effects of Exogenous Female Sex Hormones on Food Intake, Macronutrients and Body Weight in the Ovariectomized Postbreeder Female Rat.
Date of Award
Doctor of Philosophy (PhD)
Hormone replacement therapy (HRT) is chosen by a growing segment of the postmenopausal population. Mid-life body weight gain is perceived to increase further with exogenous HRT. To examine hormonal effects on caloric intake (CI), carbohydrate (CHO), FAT, protein (PRO), chocolate and body weight (BW) in a female model, Sprague-Dawley postbreeder (n = 55) rats (10 mos., 10 litters of pups) were ovariectomized (OV) and implanted with 17 $\beta$ estradiol (E) and/or progesterone (P), or placebo in three separate studies (phases) of 10 days each. Uterine weights (p =.0001) and radioimmunoassay confirmed hormonal bioactivity. The sham (S) group with placebo implant was used for comparison. In phase I, 3 food cups containing CHO, FAT, and PRO were presented ad libitum to all treatments. Estrogen decreased the rate of body weight gain (p =.001) compared to OV, P, and S with no significant differences in caloric intake (trend of estrogen p =.052). In phase II, all except S received 4 food cups; 2 CHO choices, (sweet, AIN 76 and nonsweet AIN 93), FAT and PRO. The body weight of the P and S groups compared to OV (p =.009) in phase II did not continue to increase. OV produced a carbohydrate appetite for both SW & NSW (p =.007), E&P chose 3 times more SW than NSW (p =.001). For phase III 4 caloric levels of chocolate were added (except for S). Chocolate was consumed at 40% to 53% of total caloric intake with or without HRT with reduced nutrient dense macronutrient consumption. Thus access to chocolate eliminated both the reduced rate of weight gain caused by E (phase I) and the body weight adaptation by P in phase II. Variations in % fate intake (40% to 60%) did not result in treatment differences in body composition (p =.095). The OV group which consumed the most calories from carbohydrate (p =.001), gained the most overall BW (p =.001). The rats consuming the most fat (S 57%) gained the least amount of body weight (p =.001). Caloric conversion ratios (weight gain/by caloric intake $\times$ 1000) varied among treatments (p =.003). Additional research on the metabolism of the postmenopausal female taking hormone replacement therapy is needed.
Hamilton, Jan Barton, "Effects of Exogenous Female Sex Hormones on Food Intake, Macronutrients and Body Weight in the Ovariectomized Postbreeder Female Rat." (1995). LSU Historical Dissertations and Theses. 6104.