Assessment of the Dose–Response Relationship between Meal Protein Content and Postprandial Thermogenesis: Effect of Sex and the Oral Contraceptive Pill

Abstract

Implementation of efficacious dietary interventions to regulate energy balance requires understanding of the determinants of individual response. To date, information regarding individual variability in response to elevated meal protein content is lacking. This study investigates whether sex and/or oral contraceptive pill (OCP) use play a role in the response to elevated meal protein in 21 healthy young adults (seven men, seven women not taking OCP, and seven women who were OCP users). Participants consumed each of three standardized isocaloric (590 kcal) meals of differing protein content (11, 23, 31% kcal protein). Resting energy expenditure (EE), respiratory quotient (RQ), hunger and satiety were measured at baseline (fasting) and during 180 min postprandial. Whilst significant dose–response increases in EE were observed in men, meal protein-induced EE in women without OCP reached a maximum at <23% protein. Women taking OCP reported lower postprandial fullness than women without OCP, despite similar body size, but also, most notably, no significant difference in EE response between any of the meals. Whilst the mechanisms underpinning this thermogenic inflexibility in response across a wide-range (three-fold) of protein meal content require further investigation, this highlights the need for careful consideration of factors that may influence an individual’s metabolic response to dietary interventions aimed at optimising postprandial thermogenesis for body weight regulation.

Impact of estrogens on resting energy expenditure: A systematic review

“…Disagreements were resolved by bilateral consensus. With the exception of the study by Eck et al 146 in which the methodological quality was rated as strong, corresponding to a low risk of bias, the methodological quality of all other studies [147][148][149][150][151][152][153][154] was only rated as moderate (Tables 3 and 4).…”

“…Our systematic review identified a total of 10 studies investigating the effects of medication with natural and synthetic estrogens on REE and encompassing 461 healthy normal-weight and overweight women (Tables 1 and 2). [146][147][148][149][150][151][152][153][154][155] The 10 included studies consisted of six studies in which estrogens were used in the context of HC 146,[149][150][151][152]154 and four studies in which estrogens were used in the context of MHT. 147,148,153,155 Study designs were either RCTs, 150,151,153 prospective cohort studies, 147 or cross-sectional studies.…”

“…[146][147][148][149][150][151][152][153][154][155] The 10 included studies consisted of six studies in which estrogens were used in the context of HC 146,[149][150][151][152]154 and four studies in which estrogens were used in the context of MHT. 147,148,153,155 Study designs were either RCTs, 150,151,153 prospective cohort studies, 147 or cross-sectional studies. 146,148,149,152,154,155 The sample size of each cohort with the population of interest ranged from 6 155 to 99 subjects.…”

“…estrogen used was either estradiol (E2) or conjugated equine estrogens (CEE), in the context of MHT, 147,148,153,155 or ethinyl estradiol (EE), in the context of contraception. 146,[149][150][151][152]154 E2 dose and type of application in MHT varied from 50 to 75 μg/d transdermally 147,153 to no further specification. 155 CEE dose and mode of application in MHT varied from 0.625 mg/d orally 148 to no further information.…”

“…155 CEE dose and mode of application in MHT varied from 0.625 mg/d orally 148 to no further information. 155 EE dose and form of application in contraception varied from 20 to 50 mcg/d orally 146,[149][150][151]154 to a generalized statement of inclusion of all HC methods, and thus also of progestin-only methods. 152 The type of progestin used in MHT varied between medroxyprogesterone acetate (MPA), 148,153 progesterone, 147 and no further details regarding the used progestin.…”