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

Effect of Menstrual Cycle Phase and Hormonal Contraceptives on Resting Metabolic Rate and Body Composition

The cyclical changes in sex hormones across the menstrual cycle (MC) are associated with various biological changes that may alter resting metabolic rate (RMR) and body composition estimates. Hormonal contraceptive (HC) use must also be considered given their impact on endogenous sex hormone concentrations and synchronous exogenous profiles. The purpose of this study was to determine if RMR and dual-energy X-ray absorptiometry body composition estimates change across the MC and differ compared with HC users. This was accomplished during a 5-week training camp involving naturally cycling athletes (n = 11) and HC users (n = 7 subdermal progestin implant, n = 4 combined monophasic oral contraceptive pill, n = 1 injection) from the National Rugby League Indigenous Women's Academy. MC phase was retrospectively confirmed via serum estradiol and progesterone concentrations and a positive ovulation test. HC users had serum estradiol and progesterone concentrations assessed at the time point of testing. Results were analyzed using general linear mixed model. There was no effect of MC phase on absolute RMR (p = .877), relative RMR (p = .957), or dual-energy X-ray absorptiometry body composition estimates (p > .05). There was no effect of HC use on absolute RMR (p = .069), relative RMR (p = .679), or fat mass estimates (p = .766), but HC users had a greater fat-free mass and lean body mass than naturally cycling athletes (p = .028). Our findings suggest that RMR and dual-energy X-ray absorptiometry body composition estimates do not significantly differ due to changes in sex hormones in a group of athletes, and measurements can be compared between MC phases or with HC usage without variations in sex hormones causing additional noise.

Impact of estrogens on resting energy expenditure: A systematic review

The fear of weight gain is one of the main reasons for women not to initiate or to early discontinue hormonal contraception or menopausal hormone therapy. Resting energy expenditure is by far the largest component and the most important determinant of total energy expenditure. Given that low resting energy expenditure is a confirmed predictive factor for weight gain and consecutively for the development of obesity, research into the influence of sex steroids on resting energy expenditure is a particularly exciting area. The objective of this systematic review was to evaluate the effects of medication with natural and synthetic estrogens on resting energy expenditure in healthy normal weight and overweight women. Through complex systematic literature searches, a total of 10 studies were identified that investigated the effects of medication with estrogens on resting energy expenditure. Our results demonstrate that estrogen administration increases resting energy expenditure by up to +208 kcal per day in the context of contraception and by up to +222 kcal per day in the context of menopausal hormone therapy, suggesting a preventive effect of circulating estrogen levels and estrogen administration on weight gain and obesity development.

Different Isocaloric Meals and Adiposity Modify Energy Expenditure, Clinical and Metabolomic Biomarkers During Resting and Exercise States in a Randomized Cross-over Acute Trial of Normal Weight and Overweight/obese Men

BACKGROUND

Few studies have assessed the integrative effects of diet, BMI, and exercise on postprandial changes of energy and circulating metabolic profiles.

OBJECTIVES

We aimed to assess the collective effects of three isocaloric diets high in carbohydrate (74.2% energy), fat (64.6% energy), or protein (39.5% energy) on energy expenditure, clinical and metabolomic biomarkers under resting and exercise conditions in normal-weight and overweight/obese men.

METHODS

This cross-over controlled acute trial included 20 normal-weight (BMI: 18.5- <24) and 20 overweight/obese (BMI ≥ 24 kg/m2) men aged 18-45 years. Each of three test meals was provided for two continuous days: "Resting Day" without exercise, followed by "Exercise Day" with a bicycling exercise of 50% maximal oxygen consumption (postprandial 90-120 min). Energy expenditure (exploratory outcome of primary interest) was measured using indirect calorimetry. Fasting and postprandial 2-hour serum clinical and metabolomic biomarkers (secondary interest) were measured. Mixed models were used to examine the effects of diet, time, and/or BMI category.

RESULTS

On Resting Day, no significant between-meal differences were detected for energy expenditure. However, high-carbohydrate and high-fat meals induced the highest postprandial 2-hour increase in glucose (0.34 ± 0.15 mmol/L) and triglyceride (0.95 ± 0.09 mmol/L) respectively, while high-protein meal reduced glucose (-0.48 ± 0.08 mmol/L) and total cholesterol (-0.01 ± 0.03 mmol/L, all Pdiet < 0.001). On Exercise Day, high-carbohydrate diet significantly promoted carbohydrate oxidation rate but suppressed fat oxidation rate (Pdiet < 0.05), while its postprandial glucose response was attenuated by bicycling (-0.31 ± 0.03 mmol/L, Pexercise < 0.001). 69 metabolites were identified as key features in discriminating the three meals, and overweight/obese men had more varieties of metabolites than normal-weight men.

CONCLUSIONS

Three isocaloric meals induced unique postprandial changes in clinical and metabolomic biomarkers, while exercise prevented high-carbohydrate meal induced hyperglycemia. Overweight/obese men were more responsive to the meal challenges than normal-weight men. This trial was registered at clinicaltrials.gov as NCT03231618.

Effect of oral contraceptives on energy balance in women: A review of current knowledge and potential cellular mechanisms

Body weight management is currently of major concern as the obesity epidemic is still a worldwide challenge. As women face more difficulties to lose weight than men, there is an urgent need to better understand the underlying reasons and mechanisms. Recent data have suggested that the use of oral contraceptive (OC) could be involved. The necessity of utilization and development of contraceptive strategies for birth regulation is undeniable and contraceptive pills appear as a quite easy approach. Moreover, OC also represent a strategy for the management of premenstrual symptoms, acne or bulimia nervosa. The exact impact of OC on body weight remains not clearly established. Thus, after exploring the potential underlying mechanisms by which OC could influence the two side of energy balance, we then provide an overview of the available evidence regarding the effects of OC on energy balance (i.e. energy expenditure and energy intake). Finally, we highlight the necessity for future research to clarify the cellular effects of OC and how the individualization of OC prescriptions can improve long-term weight loss management.