The Role of Estradiol and Progesterone on Appetite Regulation and Energy Balance (E2 & P4 in EB)

The purpose of this study is to further elucidate the individual and combined effects of estradiol and progesterone on appetite-regulating hormones, perceptions of appetite, energy intake, and energy expenditure over a 13 day supplementation period using a randomized controlled trial (RCT) model in males who will be supplemented with each hormone. Sixty healthy, recreationally active male participants will be randomized into one of four possible groups: placebo (PLA; 400 milligrams (mg) per day glucose polymer), estradiol only (E; 1 mg per day for 2 days & 2 mg per day of estradiol for 11 days + 300 mg Polycose), progesterone only (P; Prometrium, 100 mg per day), or combined estradiol and progesterone (E+P; 1 mg per day for 2 days & 2 mg per day of estradiol for 11 days + 300 mg Polycose for estradiol and 100 mg per day of Prometrium) for a total of ~15 per group. Participants will be provided enough daily dose of each treatment dependent on randomization for a total of 13 days and will be instructed to take each supplement orally at the same time each day for the entirety of the intervention. Participants will report to the lab on the 7th day, where they will be fed a standardized meal and then complete either an acute bout of high-intensity interval training (HIIT; 1 minute on, 1 minute off at 90% HRmax) or a period of seated rest (CTRL). Participants will return on day 12 to complete either the HIIT or CTRL session in an identical manner (whichever was not completed on day 7). Blood samples to measure appetite-regulating hormones and perceptions of appetite will be completed pre-exercise, 0-, 30-, 60-, and 120-minutes post-HIIT and CTRL. While participants are receiving the 13 day treatment, free-living energy intake will be assessed for a 3 day period (day before, day of and day after both in lab visits (HIIT/CTRL; days 6-8 and days 11-13) using the Keenoa® mobile application, and energy expenditure will be measured via thigh-worn accelerometers for the same 3 day periods. An ad libitum meal will also be provided following the HIIT and CTRL sessions.

We anticipate publishing this RCT in two separate manuscripts. Manuscript #1 will focus on the potential effects on the appetite-regulating hormones (acylated ghrelin, GLP-1, CCK) and perceptions of appetite. Manuscript #2 will focus on potential effects on energy balance from the measures of energy intake (including free-living and ad-libitum meal intake) and energy expenditure.