Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Kinesiology and Physical Education

Faculty/School

Faculty of Science

First Advisor

Tom J. Hazell

Advisor Role

Assistant Professor

Abstract

Background: Obesity rates are higher among females than males potentially due to changing food intake across the menstrual cycle. Food intake is partially regulated by circulating appetite-regulating hormones that can be influenced by the menstrual hormones estradiol and progesterone. Purpose: Examine whether changes in female sex hormones across the menstrual cycle are related to appetite-regulating hormones. Methods: 8 healthy young females were tested during the follicular, ovulatory, and luteal phases; phases were confirmed by fasting plasma hormone concentrations. Blood samples were taken after an overnight fast, as well as 30, 60, and 90 min post-prandially to test the concentrations of acylated ghrelin and active GLP-1. Perceived hunger, fullness, satisfaction, and prospective food intake were collected immediately prior to blood samples. Resting metabolic rate and substrate oxidation were tested through indirect calorimetry. Results: Menstrual cycle phase had no effect on acylated ghrelin (P=0.959) or active GLP-1 (P=0.650). Post-prandial fullness was greater during the OP compared to FP (P=0.02) and approached significance with the LP (P=0.06) but there was no difference in other perceptions of appetite. There was no effect of menstrual cycle phase on resting metabolic rate (P=0.961), carbohydrate oxidation rate (P=0.603), or fat oxidation rate (P=0.485). Conclusion: Acylated ghrelin and active GLP-1 are unlikely to explain the previously documented changes in energy intake across the menstrual cycle though perceived fullness can be elevated during the luteal phase. Taken together, this suggests that sensitivity to appetite-regulating hormones might fluctuate across the menstrual cycle.

Convocation Year

2016

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