Effects of race, cigarette smoking, and use of contraceptive medications on resting energy expenditure in young women

Effects of the Menstrual Cycle and Hormonal Contraceptive Use on Metabolic Outcomes, Strength Performance, and Recovery: A Narrative Review

The effects of female sex hormones on optimal performance have been increasingly recognized as an important consideration in exercise and sport science research. This narrative review explores the findings of studies evaluating the effects of menstrual cycle phase in eumenorrheic women and the use of hormonal contraception (oral contraceptives and hormonal intrauterine devices) on metabolism, muscular strength, and recovery in active females. Ovarian hormones are known to influence metabolism because estrogen is a master regulator of bioenergetics. Importantly, the menstrual cycle may impact protein synthesis, impacting skeletal muscle quality and strength. Studies investigating muscular strength in eumenorrheic women report equivocal findings between the follicular phase and luteal phase with no differences compared to oral contraceptive users. Studies examining recovery measures (using biomarkers, blood lactate, and blood flow) do not report clear or consistent effects of the impact of the menstrual cycle or hormonal contraception use on recovery. Overall, the current literature may be limited by the evaluation of only one menstrual cycle and the use of group means for statistical significance. Hence, to optimize training and performance in females, regardless of hormonal contraception use, there is a need for future research to quantify the intra-individual impact of the menstrual cycle phases and hormonal contraceptive use in active females.

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.

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.

Resting Energy Expenditure of Black Overweight Women in South Africa Is Lower than of White Women

BACKGROUND

Overweight affects 65% of black South African women. Effective weight management requires accurate measurement or estimation of energy expenditure.

AIMS

The study aimed to determine, among overweight women, whether measured resting energy expenditure (REE) differs between black and white participants, and the performance of REE estimation equations.

METHODS

The REE of 44 black (age 39.6 ± 9.7 years, body mass index (BMI) 35.1 ± 6.2 kg/m2) and 41 white (age 38.0 ± 11.6 years, BMI 33.9 ± 7.6 kg/m2) women was measured with indirect calorimetry and estimated with equations. Body composition was assessed with multi-frequency bioelectrical impedance analysis. Differences in REE were determined with t tests (Welch), and included adjustment for fat free mass (FFM) and BMI, and for FFM index (FFMI).

RESULTS

Measured REE was 585 kJ/day (95% CI 264-905; p = 0.0005) and 861 kJ/day (95% CI 499-1,221; p < 0.0001) lower in black than in white women when adjusted for FFM and BMI, and FFMI, respectively. Out of 14 equations, 13 underestimated REE (error range 2,261 ± 727 kJ/day (Bernstein equation, white women) to 8 ± 782 kJ/day (BMI equation, black women)).

CONCLUSIONS

Black overweight women have significantly lower REE than their white counterparts. No tested estimation equation provided satisfactory results across race/ethnicity. REE measurements or development of overweight- or race/ethnicity-specific estimation equations are recommended.

Smoking is associated with increased resting energy expenditure in the general population: The NEO study

OBJECTIVE

Animal studies and human studies in small selected populations have shown a positive association between nicotine smoking and resting energy expenditure (REE), but data in large cohorts are lacking. We aimed to investigate the association between smoking behavior and REE in a large, population-based study.

DESIGN

Population-based cross-sectional study.

METHODS

In this cross-sectional analysis of baseline measurements from the Netherlands Epidemiology of Obesity (NEO) study (n=6673), we included participants with REE measurement by indirect calorimetry who were not using lipid or glucose lowering drugs (n=1189). We used linear regression analysis to examine the association of smoking status (never, former, occasional, current smoker) and smoking quantity (pack years) with REE per kilogram (kg) fat free mass (FFM) and with REE adjusted for FFM. Models were adjusted for age, sex, ethnicity, educational level, physical activity, energy intake and body mass index (BMI).

RESULTS

Mean (standard deviation, SD) age was 55.2 (5.9) years and BMI was 26.3 (4.4) kg/m(2). 60% of the participants were women. Mean (SD) REE/FFM (kcal/day/kg FFM) was for male never smokers 25.1 (2.0), male current smokers 26.4 (2.8), female never smokers 28.9 (2.5) and female current smokers 30.1 (3.7). After adjustment, only current smokers had a higher REE/FFM (mean difference 1.28, 95% CI 0.64, 1.92), and a higher REE adjusted for FFM (mean difference 60.3 kcal/day, 95% CI 29.1, 91.5), compared with never smokers. There was no association between pack years and REE/FFM (mean difference -0.01, 95% CI -0.06, 0.04) or REE adjusted for FFM (mean difference 0.2, 95% CI -2.4, 2.8) in current smokers.

CONCLUSION

Current smoking is associated with a higher resting energy expenditure compared with never smoking in a large population-based cohort.

Cigarette smoking induces overexpression of a fat-depleting gene AZGP1 in the human

BACKGROUND

Smokers weigh less and have less body fat than nonsmokers. Increased body fat and weight gain are observed following smoking cessation. To assess a possible molecular mechanism underlying the inverse association between smoking and body weight, we hypothesized that smoking may induce the expression of a fat-depleting gene in the airway epithelium, the cell population that takes the brunt of the stress of cigarette smoke.

METHODS

To assess whether smoking up-regulates expression in the airway epithelium of genes associated with weight loss, microarray analysis was used to evaluate genes associated with fat depletion in large airway epithelial samples obtained by fiberoptic bronchoscopy from healthy smokers and healthy nonsmokers. As a candidate gene we further evaluated the expression of alpha(2)-zinc-glycoprotein 1 (AZGP1), a soluble protein that stimulates lipolysis, induces a reduction in body fat in mice, is associated with the cachexia related to cancer, and is known to be expressed in secretory cells of lung epithelium. AZGP1 protein expression was assessed by Western analysis and localization in the large airway epithelium by immunohistochemistry.

RESULTS

Both microarray and TaqMan analysis demonstrated that AZGP1 messenger RNA levels were higher in the large airway epithelium of healthy smokers compared to healthy nonsmokers (p < 0.05, all comparisons). Western analysis of airway biopsy specimens from smokers compared with those from nonsmokers demonstrated up-regulation of AZGP1 at the protein level, and immunohistochemical analysis demonstrated up-regulation of AZGP1 in secretory as well as neuroendocrine cells of smokers.

CONCLUSIONS

In the context that AZGP1 is involved in lipolysis and fat loss, its overexpression in the airway epithelium of chronic smokers may represent one mechanism for the weight difference in smokers vs nonsmokers.

Racial differences in correlates of misreporting of energy intake in adolescent females

OBJECTIVE

To determine the extent of misreporting of energy intake (EI) and its anthropometric, demographic, and psychosocial correlates in a bi-racial cohort of young women.

RESEARCH METHODS AND PROCEDURES

This was a cross-sectional study of 60 black and 60 white young women, 18 to 21 years old, enrolled in a longitudinal study. Total energy expenditure was assessed using doubly labeled water. Self-reported EI was obtained from 3-day food records. BMI was computed from height and weight. Fat mass was assessed by DXA. Multivariate analyses examined racial differences on the extent of misreporting and its effect on other potential correlates of misreporting. Race-specific step-wise linear regression analysis was performed to examine the effect of BMI, parental education, and drive for thinness on misreporting of EI.

RESULTS

More white women tended to under-report EI than black women (22% vs. 13%, p = 0.07). In black women, under-reporting was significantly (p = 0.01) associated with drive for thinness score but was only marginally (p = 0.1) associated with BMI. Each point increase in drive for thinness score was associated with under-reporting by 40 kcal/d. In white women, under-reporting was significantly (p = 0.03) associated with higher parental education by 440 kcal/d and also only marginally (p = 0.09) with BMI.

DISCUSSION

This tendency for under-reporting of EI limits the use of self-reported EI in studying energy balance in free-living subjects. Most black and almost all white women in their late teens significantly under-reported their EI, whereas under-reporting was not as evident among lean young black women.

Smoking, oxidative stress and inflammation: impact on resting energy expenditure in diabetic nephropathy

BACKGROUND

Inflammation is associated with increased resting energy expenditure (REE) in patients with chronic kidney disease. Oxidative stress, on the other hand, appears not to increase REE. Smoking is a common mechanism for generating oxidative stress and inflammation. Whether smokers have increased REE and if so, whether it is accounted for by the pro-oxidant and inflammatory state is not known.

METHODS

A case control study of 11 smokers and 24 non-smokers with overt diabetic nephropathy was performed to evaluate the chronic effect of smoking on REE. REE (indirect calorimetry), glomerular filtration rate (iothalamate clearance), markers of oxidative stress (urinary and plasma malondialdehyde (MDA), and protein carbonyls) and inflammation (C-reactive protein, tumor necrosis factor-alpha, interleukin-6) were measured on two occasions four months apart.

RESULTS

Biomarkers of inflammation (C-reactive protein) and oxidative stress (urinary and plasma MDA) were increased in smokers. REE was increased in smokers, 24.3 kcal/kg/day compared to 21 kcal/kg/day (p = 0.009) in non-smokers. After adjusting for age, GFR, MDA, C-reactive protein, and hemoglobin A1C the difference in REE between the two groups persisted (adjusted difference 3.51 kcal/kg/d, 95% confidence interval 0.59-6.45, p = 0.020).

CONCLUSION

Patients with overt diabetic nephropathy who smoke have a higher REE, oxidative and inflammatory state. Elevated REE is not attributable to heightened oxidative stress and inflammatory state. Smoking is an independent risk factor for elevated REE in patients with diabetic nephropathy and provides an additional mechanism by which it may lead to poor outcomes.

Lower resting metabolic rate in the elderly may not be entirely due to changes in body composition

OBJECTIVE

To investigate whether or not the lower resting metabolic rate (RMR) in the elderly is entirely due to changes in body composition.

DESIGN

Cross-sectional data of 132 female (age 69.9+/-5.5 y, body mass index (BMI) 26.5+/-4.0 kg/m(2)) and 84 male (age 68.9+/-5.1 y, BMI 26.1+/-2.8 kg/m(2)) participants of the longitudinal study on nutrition and health status in an aging population of Giessen, Germany, as well as that of 159 young women (age 24.8+/-3.0 y, BMI 21.1+/-2.5 kg/m(2)) and 67 young men (age 26.8+/-3.4 y, BMI 23.3+/-2.4 kg/m(2)) were analysed. RMR was measured by indirect calorimetry after an overnight fast and body composition was estimated by bioelectrical impedance analysis and predictive equations from the literature. Analysis of covariance was used to adjust RMR for body composition, body fat distribution and smoking habits. Additionally, RMR that is to be expected theoretically, was calculated on the basis of the subjects' body composition and the specific metabolic rate of the different organs and was compared to measured RMR.

RESULTS

Compared to young subjects adjusted RMR was significantly lower in elderly women (5432+/-82 vs 5809+/-70 kJ/day, P<0.01) and men (6971+/-99 vs 7558+/-121 kJ/day, P<0.001). In both elderly women and men, measured RMR was markedly lower than calculated RMR (-625+/-404, -515+/-570 kJ/day). By contrast, measured and calculated RMR were nearly the same in young men (159+/-612 kJ/day); in young women the difference between measured and calculated RMR was only -300+/-457 kJ/day. In both sexes, these differences are significantly larger in the elderly when compared to young adults.

CONCLUSION

These results support the point of view that the decline in RMR with advancing age cannot be totally due to changes in body composition.

Development and cross-validation of a prediction equation for estimating resting energy expenditure in healthy African-American and European-American women

OBJECTIVE

To develop, validate, and cross-validate a formula for predicting resting energy expenditure (REE) in African-American and European-American women.

DESIGN

A cross-sectional study of REE in women. Participants were randomly assigned to one of two groups. One group served to develop and validate a new equation for predicting REE while the second was used to cross-validate the prediction equation. The accuracy of the equation was compared to several existing formulae.

SETTING

University metabolic laboratory, Memphis, TN, USA.

SUBJECTS

Healthy, premenopausal African-American and European-American women between 18 and 39 y of age. The validation sample included 239 women (age: 28.4 y, wt: 70.7 kg, body mass index (BMI): 25.2 kg/m(2), REE: 5840 kJ/day), while the cross-validation sample consisted of 232 women (age: 27.5 y, wt: 70.7 kg, BMI: 25.2 kg/m(2), REE: 5784 kJ/day).

RESULTS

The prediction equation derived from the current sample, which included adjustments for ethnicity, was the only formula that demonstrated a high level of accuracy for predicting REE in both African-American and European-American women. The mean difference between REE predicted from the new formula and measured REE was 28 kJ/day (s.d.=668) for European-American women and 142 kJ/day (s.d.=584) for African-American women.

CONCLUSIONS

Previous equations for predicting energy needs may not be appropriate for both African-American and European-American women due to ethnic differences in REE. A new equation that makes adjustments in predicted REE based on ethnicity is recommended for determining energy needs in these groups (Predicted REE (kJ/day)=616.93-14.9 (AGE (y))+35.12 (WT (kg))+19.83 (HT (cm))-271.88 (ETHNICITY: 1=African American; 0=European American)).

SPONSORSHIP

Support for this study was provided by Grant #HL53261 from the National Heart, Lung, and Blood Institute.

Cigarette smoking is associated with energy balance in premenopausal African-American adult women differently than in similarly aged white women

OBJECTIVE

To investigate the differential association of cigarette smoking with energy balance in African-American and white premenopausal women.

DESIGN

Cross-sectional study of energy balance, weight, and smoking in women.

SUBJECT

A total of 374 women: 191 African-American (mean age=29.8+/-6.5 y) and 183 white women (mean age=28.9+/-7.1 y).

MEASUREMENTS

Weight, cigarette smoking habits, resting energy expenditure, dietary intake, and physical activity.

RESULTS

There were no significant differences in dietary intake by race or smoking status. The model for physical activity was significant (P=0.0004), with body mass index (BMI) having the largest effect on activity (P<0.001). Smoking status was related to activity, with the heaviest smokers reporting more activity than nonsmokers (P=0.008) or light smokers (P=0.028). The model for resting energy expenditure (REE) was significant (P<0.0001), with the largest again being BMI (P<0.001). There was also an interaction between ethnicity and smoking status (P<0.0001) such that African-American nonsmokers and light smokers tended to have lower REE than several other groups, most often the African-American moderate heavy smokers. The model for BMI was significant (P<0.0001) with an interaction for ethnicity and smoking status (P=0.0009). African-American nonsmokers and light smokers had significantly higher BMIs than most of the other groups.

CONCLUSION

African-American women who were the heaviest smokers had a lower adjusted BMI than the heaviest smoking white women. This effect, at least partially, may be related to an increased REE in the African-American smoking women. While energy intake did not appear to be important in this relationship, energy expended in physical activity appeared to be increased with smoking, as was REE.