Energetic factors and seasonal changes in ovarian function in women from rural Poland

Size and Shape: Morphology's Impact on Human Speed and Mobility

While human sexual dimorphism is generally expected to be the result of differential reproductive strategies, it has the potential to create differences in the energetics of locomotion and the speed at which each morph travels, particularly since people have been shown to choose walking speeds around their metabolic optimum. Here, people of varying sizes walked around a track at four self-selected speeds while their metabolic rate was collected, in order to test whether the size variation within a population could significantly affect the shape of the optimal walking curve. The data show that larger people have significantly faster optimal walking speeds, higher costs at their optimal speed, and a more acute optimal walking curve (thus an increased penalty for walking at suboptimal speeds). Bigger people who also have wider bitrochanteric breadths have lower metabolic costs at their minimum than bigger people with a more narrow bitrochanteric breadth. Finally, tibia length significantly positively predicts optimal walking speed. These results suggest sex-specific walking groups typical of living human populations may be the result of energy maximizing strategies. In addition, testable hypotheses of group strategies are put forth.

Salivary concentration of progesterone and cortisol significantly differs across individuals after correcting for blood hormone values

Between-individual variation of salivary progesterone (P4) and cortisol levels does not always closely reflect blood hormone concentrations. This may be partly a function of individual differences in salivary hormone excretion. We tested whether time of day at sampling and ethnicity contributed to individual variation in salivary hormones after adjusting for blood hormone levels. Forty-three Caucasian and 15 Japanese women (18-34 years) collected four sets of matched dried blood spot (DBS) and saliva specimens across a menstrual cycle (N = 232 specimen sets). Linear fixed-effects (LFE) models were used to estimate the effects of diurnal variation and ethnicity on salivary P4 and cortisol while adjusting for DBS levels. For each hormone, women with exclusively positive or negative residuals (unexplained variance) from the LFE models were categorized as high- or low-saliva-to-DBS hormone ratio (SDR; high or low salivary secretors), respectively. We found that salivary P4 (P < 0.05) was significantly higher in early morning compared to the afternoon, after controlling for DBS levels, ethnicity, and BMI. After further adjusting for this diurnal effect, significant individual variation in salivary P4 and cortisol remained: sixteen and nine women, respectively were categorized as low or high salivary secretors for both hormones (P < 0.001), suggesting systematic individual-specific variation of salivary hormonal concentration. We conclude that when saliva is used to quantify P4 or cortisol levels, time of day at sampling should be controlled. Even with this adjustment, salivary P4 and cortisol do not closely mirror between- individual variation of serum P4 and cortisol in a substantial proportion of individuals.

Teen motherhood in cross-cultural perspective

Teen motherhood is the prevalent childbearing pattern in most traditional populations. Yet early motherhood is associated with negative biological and social outcomes in the developed world. We review the teen pregnancy literature in light of this discrepancy, emphasizing two core debates. The first debate centers on whether teens have poor pregnancy outcomes compared to older women, and whether negative outcomes are biologically based. Second, we consider the debate over the confounding effects of socio-economic conditions associated with being young. When teens are considered as a group, results are inconsistent across studies. When teens are disaggregated by age, the strongest finding across studies is that biological risk is concentrated in only the youngest of mothers. Negative consequences are associated with teen motherhood not because of chronological age per se, but because of relative developmental maturity and the availability of non-maternal support. In most traditional societies as well as in some sectors of developed societies, teen motherhood occurs within the context of extended kin networks and is subsidized through reliable economic and childcare assistance. Child-rearing practices, rather than pregnancy per se, may explain much of the discrepancy in the prevalence, success and attitudes toward teen motherhood in traditional and developed societies.

Fertility, body size, and shape: An empirical test of the covert maternal depletion hypothesis

In populations with limited resources, high-reproductive effort may lead to poor nutritional status of the mother (the maternal depletion syndrome), whereas in well-nourished populations woman's body weight tends to increase after each pregnancy. However, in affluent populations, women's body shape may change due to mobilization of polyunsaturated fatty acids (PUFAs) from the lower parts of their bodies to meet the needs of the developing child (the "covert maternal depletion"). We studied relationships between reproductive history traits and body size and shape for 296 rural, parous women in good nutritional status (mean body mass index, BMI = 27.9, SD = 5.94), aged 22-85 (mean 47.8, SD = 16.34) from southern Poland. Body mass adjusted for age, age of menarche, body height, and similarly adjusted BMI were each positively related to the number of children born by a woman (R = 0.13, P = 0.02 and R = 0.13, P = 0.02, respectively). Waist and hip circumferences, adjusted for confounders, did not show statistically significant relationships with the number of children. Moreover, groups with low and high parity did not significantly differ in hip/BMI and waist/BMI ratios, which were proposed to be indicators of covert form of maternal depletion (after controlling for overall body fatness and age). In conclusion, parity caused a slightly higher body mass and BMI later in life. However, parity did not lead to covert maternal depletion, perhaps because women in this population have relatively high-dietary intake of PUFAs.

Adult height, insulin, and 17beta-estradiol in young women

BACKGROUND

Adult height and insulin are thought to modify the development of breast cancer. However, little is known about the association between height and 17beta-estradiol, a key factor in breast carcinogenesis, and whether insulin modifies such an association.

METHODS

Among 204 healthy women, ages 25 to 35 years, who participated in the Energy Balance and Breast Cancer Aspect I study, adult height (in centimeters) and fasting serum concentrations of insulin (pmol/L) were measured. 17beta-Estradiol concentrations were measured in daily saliva samples throughout an entire menstrual cycle through RIA. Age and multivariate linear regression models were used to study the association between adult height and 17beta-estradiol levels throughout an entire menstrual cycle and whether serum levels of fasting insulin may modify such an association.

RESULTS

The women had a mean age of 30.7 years, adult height of 166.9 cm, and serum insulin of 85.7 pmol/L. For each increase of one SD in insulin levels in the upper tertile of adult height, the adjusted level of 17beta-estradiol increased by 3.1 pmol/L (95% confidence interval, 1.1-5.2), equivalent to a 17.3% higher mean average concentration of 17beta-estradiol. Women with an adult height > or =170 cm (upper tertile) and insulin levels >101 pmol/L (upper quartile) experienced, on average, 41% higher 17beta-estradiol levels throughout the entire menstrual cycle compared with women with the same adult height and insulin levels <101 pmol/L.

CONCLUSION

Our findings support that premenopausal levels of 17beta-estradiol vary in response to adult height and insulin levels, of possible importance for breast cancer risk.

Body fat, energy balance and estradiol levels: a study based on hormonal profiles from complete menstrual cycles

BACKGROUND

Female fecundity is regulated by nutritional status. Although widely cited, this hypothesis is not strongly supported by empirical data from non-obese, healthy women of reproductive age.

METHODS

Healthy, reproductive aged women (n = 141) from Southern Poland collected daily morning saliva samples for one complete menstrual cycle. Levels of 17-beta-estradiol were analyzed by radioimmunoassay. Anthropometric measurements, including body fat percentage, were taken randomly with respect to phase of the menstrual cycle. Energy balance was specified based on changes in body fat percentage from the beginning to the end of the observation period.

RESULTS

Women with very low and high body fat had significantly lower levels of E2 compared with women with low and average body fat. In women of very low to average body fat, a 10% increase in body fat was associated with a 5-7 pmol/l increase in estradiol levels. The association between fat percentage and E2 was even stronger in women with positive energy balance, who also showed significant differences between body fat groups in estradiol profiles across whole the menstrual cycle. No such relationship was found in women with negative energy balance.

CONCLUSIONS

In healthy women, we found a non-linear association between body fat and estradiol levels. Both very low and high body fat was associated with decreased estradiol levels. The relationship between estradiol and body fat was strongly influenced by women's energy balance.

Challenges inherent to t'ai chi research: part I--t'ai chi as a complex multicomponent intervention

In this, the first of 2 companion papers, we present a framework for viewing t'ai chi as a complex, multicomponent intervention that integrates numerous physical, cognitive, and ritualistic components. We discuss how the richness and complexity of t'ai chi poses challenges related to the traditional distinction between specific versus nonspecific effects, the development and interpretation of valid sham controls, and more generally, to the reductionist causal approach of attributing observed outcomes to single, independent component factors. We also discuss parallels between t'ai chi research and the emerging field of whole systems research, and how t'ai chi research may benefit from the use of an ecologic framework. In a second, companion paper, we discuss additional challenges inherent in defining the t'ai chi intervention itself, and more comprehensively outline the benefits and limitations of commonly used clinical research designs to evaluate the efficacy and safety of t'ai chi.

Weight change and ovarian steroid profiles in young women

OBJECTIVE

To investigate possible short-term effects of voluntary weight loss on ovarian steroid profiles in young women, in light of better established long-term effects in older women.

DESIGN

We tested for an association of voluntary weight change over the course of a menstrual cycle with salivary E(2) and P profiles in the same menstrual cycle.

SETTING

Students were recruited in a college residence hall, and they provided daily saliva samples to a researcher living nearby.

PATIENT(S)

The 65 women who participated were all college students and ranged in age between 18 and 23 years.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Weight was assessed in the first week of the menstrual cycle and first week of the following menstrual cycle. Estradiol and P were measured by radioimmunoassay in daily saliva samples.

RESULT(S)

We did not detect a suppressive effect of weight loss on the overall level of either hormone. However, we did find evidence for more distinct follicular and luteal E(2) peaks in women who gained weight. Peak luteal P also arrived about 2 days earlier in women who gained weight.

CONCLUSION(S)

This finding adds to evidence that short-term response of ovarian function to weight loss in young women is less pronounced than long-term response in older women.

Interpopulation, interindividual, intercycle, and intracycle natural variation in progesterone levels: a quantitative assessment and implications for population studies

Methodological challenges in studying sex steroid hormones in premenopausal women result from the existence of variation at three levels: among women from the same population, among menstrual cycles recorded for women at different times of the year, and among days of the same cycle. We partitioned, for a Polish rural population, the natural, nonpathological, variation in salivary progesterone concentrations (measured during 14 days of the luteal phase) into the intracycle component (which accounts for 65% of the total variation) and the among-cycle component (the remaining 35% of the total variation). Out of the among-cycle variation in salivary progesterone, as much as 46% is expressed as differences among individual women (interindividual component); the remaining 54% of variation is due to differences among cycles of individual women (intercycle, within-women component). Such intercycle variation is probably caused by a seasonality of agricultural workload and is much higher than in nonseasonal, industrial populations. We also used bootstrap analyses to generate heuristic recommendations for choosing sample sizes of the number of subjects, number of cycles per woman, and number of days per cycle. Studies in populations with seasonal lifestyles should rely on measurements of at least three cycles per woman. Given the substantial intracycle amplitude in hormone levels to reliably assess biologically and medically relevant variation in ovarian function, at least 7-8 days/cycle should be measured.

CYP17 genotypes differ in salivary 17-beta estradiol levels: a study based on hormonal profiles from entire menstrual cycles

Variation in the levels of sex-steroid hormones results from differences in developmental conditions, adult lifestyle, and genetic polymorphism. Genes involved in sex-steroid biosynthesis have been implicated to influence levels of hormones in premenopausal women, but the results were inconclusive. We tested variation among women in levels of salivary estradiol (E(2)) corresponding to CYP17 genotypes. CYP17 encodes cytochrome P450c17alpha, which mediates two enzymes important in E(2) synthesis. In contrast to the earlier studies that relied on one or a few samples for assessing the E(2) levels of an individual woman, our study is based on daily collected saliva samples for one entire menstrual cycle. Sixty Polish women, ages 24 to 36 years, with regular menstrual cycles and no reported fertility problems participated in the study. Women with A2/A2 genotype had 54% higher mean E(2) levels than women with A1/A1 genotype (P = 0.0001) and 37% higher than women with A1/A2 genotype (P = 0.0008). Heterozygous A1/A2 women had 13 % higher E(2) levels than homozygous A1/A1 women (but this difference was significant only in a nonparametric test). Levels of E(2) during the day with highest E(2) (day -1) were 72% higher in A2/A2 compared with A1/A1 (P = 0.01) and 52 % higher compared with A1/A2 (P = 0.03). Our results suggest that CYP17 genotype may serve as a biomarker of endocrine function in women of reproductive age. (Cancer Epidemiol Biomarkers Prev 2006;15(11):2131-5).

Low high-density lipoprotein cholesterol may signal breast cancer risk: recent findings and new hypotheses

Increasing bodyweight among women worldwide seems to be associated with a proportional rise in the number of women developing breast cancer. It is of utmost importance to obtain reliable biomarkers that may help clinicians to identify susceptible individuals among the growing population of women with excess adiposity. Our recent studies, reviewed within this article, support that adiposity-related metabolic disorders may represent high-risk phenotypes; specifically, we conclude that a low level of high-density lipoprotein cholesterol may be a reliable marker for breast cancer risk among overweight women. We tested our hypothesis among a large number of overweight women in the Norwegian Three County Cohort and the Norwegian cross-sectional study, the Energy Balance and Breast cancer Aspects (EBBA-I) study. Future studies should explore how genetic, environmental and behavioral factors may increase the susceptibility of overweight women to breast cancer, and how we can successfully establish targeted preventive strategies.

Potential applications of urinary C-peptide of insulin for comparative energetics research

The study of comparative energetics offers a valuable way to identify broad ecological principles and assess the functional significance of energetic adaptations during the course of evolution. Yet, the quantification of energetic status for nonhuman primates under natural conditions remains one of the most challenging aspects of comparative energetics research. Here, we report on the development of a noninvasive field method for measuring energetic status in great apes, humans, and possibly other nonhuman primates. Specifically, we have explored measurement of a urinary metabolite of insulin (C-peptide) as a physiological marker of energetic condition in chimpanzees and orangutans. We performed three validation studies and successfully measured C-peptide in urine samples from captive chimpanzees, wild chimpanzees, and wild orangutans. Urinary C-peptide measures gave indications of being a reliable signal of energetic status in both species. For chimpanzees and orangutans in the wild, baseline urinary C-peptide levels were higher during periods of fruit abundance than periods of low fruit availability. Urinary C-peptide levels were also higher for well-fed captive chimpanzees compared with wild chimpanzees. Although sample size was small, top-ranking male chimpanzees showed higher C-peptide levels in the wild than low-ranking males only during the period of fruit abundance. These preliminary results indicate that further development of the urinary C-peptide method could expand opportunities to quantify energetic condition for great apes in the wild and generate new data for comparative research. We highlight specific applications for studying great ape reproduction as well as the nutritional ecology of human foragers.

Childhood conditions influence adult progesterone levels

BACKGROUND

Average profiles of salivary progesterone in women vary significantly at the inter- and intrapopulation level as a function of age and acute energetic conditions related to energy intake, energy expenditure, or a combination of both. In addition to acute stressors, baseline progesterone levels differ among populations. The causes of such chronic differences are not well understood, but it has been hypothesised that they may result from varying tempos of growth and maturation and, by implication, from diverse environmental conditions encountered during childhood and adolescence.

METHODS AND FINDINGS

To test this hypothesis, we conducted a migrant study among first- and second-generation Bangladeshi women aged 19-39 who migrated to London, UK at different points in the life-course, women still resident in Bangladesh, and women of European descent living in neighbourhoods similar to those of the migrants in London (total n = 227). Data collected included saliva samples for radioimmunoassay of progesterone, anthropometrics, and information from questionnaires on diet, lifestyle, and health. Results from multiple linear regression, controlled for anthropometric and reproductive variables, show that women who spend their childhood in conditions of low energy expenditure, stable energy intake, good sanitation, low immune challenges, and good health care in the UK have up to 103% higher levels of salivary progesterone and an earlier maturation than women who develop in less optimal conditions in Sylhet, Bangladesh (F9,178 = 5.05, p < 0.001, standard error of the mean = 0.32; adjusted R(2) = 0.16). Our results point to the period prior to puberty as a sensitive phase when changes in environmental conditions positively impact developmental tempos such as menarcheal age (F2,81 = 3.21, p = 0.03) and patterns of ovarian function as measured using salivary progesterone (F2,81 = 3.14, p = 0.04).

CONCLUSIONS

This research demonstrates that human females use an extended period of the life cycle prior to reproductive maturation to monitor their environment and to modulate reproductive steroid levels in accordance with projected conditions they might encounter as adults. Given the prolonged investment of human pregnancy and lactation, such plasticity (extending beyond any intrauterine programming) enables a more flexible and finely tuned adjustment to the potential constraints or opportunities of the later adult environment. This research is the first, to our knowledge, to demonstrate a postuterine developmental component to variation in reproductive steroid levels in women.

Habitual physical activity and estradiol levels in women of reproductive age

Variation in the risk of breast cancer observed among women and among populations may be explained by variation in lifetime exposure to estrogens. The suppressive effect of exercise on estradiol levels in women is well documented, but it is unknown whether habitual (i.e. typical daily) physical activity has a similar effect. Epidemiological data suggest that physical activity is one of the few modifiable factors capable of reducing the risk of breast cancer in women. We investigated whether variation in the amount of habitual activity corresponds to variation in estradiol levels in women of reproductive age. One hundred and thirty-nine regularly menstruating women 24-37 years of age collected daily saliva samples for one complete menstrual cycle and kept a daily log of physical activity. Saliva samples were analyzed for concentration of estradiol. We observed a negative relationship between habitual physical activity and salivary levels of estradiol. Mean estradiol was 21.1 pmol/l in the low, 17.9 pmol/l in the moderate and 16.6 pmol/l in the high activity group (all pairwise differences were statistically significant at P<0.009). A strong association exists between physical activity and levels of estradiol among women of reproductive age. A modern lifestyle, characterized by reduced physical activity, may therefore contribute to a rise in the levels of estradiol produced during menstrual cycles and thus to higher cumulative lifetime exposure to estradiol, resulting in a higher risk of breast cancer.

Association of physical activity with development of uterine leiomyoma

The relation between physical activity and uterine leiomyomata (fibroids) has received little study, but exercise is protective for breast cancer, another hormonally mediated tumor. Participants in this study were randomly selected members of a health plan based in Washington, DC, aged 35-49 years (734 African Americans, 455 Whites) enrolled between 1996 and 1999. Fibroid status was based on ultrasound screening. Physical activity was based on detailed interview questions. Logistic regression with adjustment for body mass index and other risk factors showed that women in the highest category of physical activity were significantly less likely to have fibroids (odds ratio = 0.6, 95% confidence interval = 0.4, 0.9 for the highest vs. the lowest category (equivalent to approximately > or =7 hours/week vs <2 hours/week)). There was a dose-response pattern; a significant trend was seen for both African-American and White women. A multistate Bayesian analysis indicated that exercise was associated with tumor onset more strongly than with tumor growth. When data for women who reported major fibroid-related symptoms were excluded, results remained essentially unchanged, suggesting that the observed association could not be attributed to reverse causation (fibroids preventing exercise). The authors concluded that regular exercise might help women prevent fibroids.

Menstruation does not cause anemia: endometrial thickness correlates positively with erythrocyte count and hemoglobin concentration in premenopausal women

Menstruation has often been cited as a risk factor for iron-deficiency anemia. This study tested whether normal, premenopausal women's luteal endometrial thickness (ET) was associated with their red blood cell count (RBC) and hemoglobin concentrations (Hg), and therefore whether a high ET put women at risk for anemia. Endometrial thickness can be considered a reasonable proxy for menstrual blood loss in normal women. Twenty-six healthy women from the Mogielica Human Ecology Study Site in Poland, aged 20-40 years (29 +/- 5.3 years, mean +/- SD), were selected. Subjects' ET was measured by transvaginal ultrasound in the luteal phase of the menstrual cycle, and their red blood cell count and hemoglobin concentrations were measured by fasting morning blood samples. Controlling for day of ET measurement, RBC and Hg were positively correlated with ET (r(2) = 0.24, P = 0.05; r(2) = 0.25, P = 0.04, respectively). We propose that, contrary to popular understanding, a thicker endometrium suggests greater iron reserves, rather than greater risk for anemia, in healthy women.

Fatness at birth predicts adult susceptibility to ovarian suppression: an empirical test of the Predictive Adaptive Response hypothesis

Poor fetal environments are thought to produce adaptive changes in human developmental trajectories according to the Predictive Adaptive Response hypothesis. Although many studies have demonstrated correlations between indicators of fetal environment and negative adult health outcomes, the adaptive significance of these outcomes is unclear. Our study explicitly tests the adaptive nature of fetal programming in humans. We show that differences in nutritional status at birth are associated with adaptive differences in the sensitivity of adult ovarian function to energetic stress. Women who were born as relatively fat babies do not exhibit ovarian suppression in response to moderate levels of physical activity at adulthood, in contrast to women who were born as skinnier babies. The levels of estradiol in women born in the highest tertile of ponderal index (an indicator of neonatal nutritional status) were 37% and 46% higher, respectively, than levels of estradiol in women born in the low and middle ponderal index tertiles. These findings suggest that fetal programming of reproductive function results in developmentally plastic, but essentially adaptive, shifts in set points of ovarian response to energetic stress, such that women who were gestated under conditions of energetic constraint show greater sensitivity to energetic stress in adulthood. Our results have practical implications in terms of behavioral strategies for reducing the risk of breast cancer. We suggest that the amount of activity necessary to reduce levels of estrogen, which may in turn reduce cancer risk, can depend on a woman's nutritional status at birth.

High tea consumption diminishes salivary 17beta-estradiol concentration in Polish women

We hypothesized that among reproductive-age women consuming large quantities of tea, the production of estradiol would be suppressed. It has been shown that catechins and theaflavines, the major constituents of tea, inhibit aromatase, an enzyme which catalyses the conversion of androgens to oestrogens. Our study included Polish women living in urban (n 61) and rural (n 48) areas. Women collected daily saliva samples for one complete menstrual cycle and filled out dietary questionnaires. Saliva samples were analysed by RIA for concentration of 17beta-estradiol (E2). Women with high (above the median) average daily consumption of black tea had reduced levels of salivary E2 in comparison with women who drank less black tea (below the median). This effect was observed within the whole study group, as well as separately within urban (P=0.0006) and rural (P=0.013) groups. High intake of the sum of subclasses of tea catechins and epigallocatechin gallate, assessed using the United States Department of Agriculture database (http://www.nal.usda.gov), was also associated with lower concentrations of E2 within all women (P=0.01 and P=0.0001, respectively) and within the urban group (P=0.0001 and P=0.004, respectively). Similar relationships were observed between the sum of subclasses of theaflavines and thearubigines and E2 levels for the whole group (P=0.002) and for urban women (P=0.02). Women with high consumption of tea had lower levels of E2 concentration throughout the entire menstrual cycle. These results may have implications for reducing hormone-related cancer risk by a relatively easy dietary intervention.

Daughters increase longevity of fathers, but daughters and sons equally reduce longevity of mothers

Reproduction is energetically and physiologically expensive, and an individual investing resources into producing offspring should suffer costs such as deterioration in health condition and possibly shorter life span. Since the energetic and nutritional demands of pregnancy and breastfeeding render reproductive costs much higher in women than in men, women with a large number of children should show signs of deterioration in condition, while men with large families should not. However, whether reproductive costs reduce longevity in women is still questionable, and in men this issue has not been adequately addressed. In addition, since sons are energetically more expensive to produce than daughters, having sons should have a more pronounced negative impact on maternal longevity than having daughters. Here we document a striking disparity in the impact of children on the life span of mothers and fathers in a Polish rural population. We show for the first time that number of daughters was positively related to a longer life span of their fathers, increasing their longevity on average by 74 weeks per daughter born, while number of sons did not have a significant effect on paternal longevity. In contrast, in women, the number of daughters and number of sons reduced maternal longevity and did so to the same extent, on average by 95 weeks per son or daughter, indicating that for women, the costs of having sons and daughters are similar.

Anthropometric data indicate nutritional homogeneity in Hadza foragers of Tanzania

We analyzed body mass index (BMI = wt/height(2)) and percent body fat (BF%) in adults of the Hadza, an egalitarian society with a strong food-sharing ethic, to examine variation in energetic status in relation to sex, age, and time of year. Data collected from 26 camps over six field seasons gave a cross-sectional sample of 238 males and 235 females and a small longitudinal sample (n = 54). We found that mean BMI showed no sex difference [20.1 +/- 1.6 (SD) kg/m(2) for males and 20.3 +/- 2.2 kg/m(2) for females] and remained similar, regardless of age or time of year. Mean BF% showed a significant sex difference, as expected [10.6 +/- 3.2 (SD) % for males and 19.0 +/- 7.0% for females (P < 0.0001)], with two significant age departures from uniformity: (1) males in the prime age group (30-45 years, n = 79) had a higher mean BF% (11.7%) compared to other ages (P < 0.03), and (2) females in the extreme elderly age group (> 75 years, n = 11) had a lower mean BF% (11.3%) compared to other ages (P < 0.004). In the longitudinal sample, we found no significant change over time in mean BMI or BF%. However, relative change in BF% fluctuated within individuals by as much as 20% of initial values for both sexes. Taken collectively, our results support the idea of broad nutritional homogeneity among the Hadza, but indicate that subtle, potentially important differences in energetic condition exist as well.

Adaptive variation in testosterone levels in response to immune activation: empirical and theoretical perspectives

High testosterone levels reflect investment in male reproductive effort through the ability to produce and maintain muscle tissue and thus augment mate attraction and competitive ability. However, high testosterone levels can also compromise survivorship by increasing risk of prostate cancer, production of oxygen radicals, risk of injury due to hormonally-augmented behaviors such as aggression, violence and risk taking, reduced tissue and organ maintenance, negative energy balance from adipose tissue catabolism, and suppression of immune functions. Here, I briefly discuss how inter- and intra-individual variation in human male testosterone levels is likely an adaptive mechanism that facilitates the allocation of metabolic resources, particularly in response to injury, illness or otherwise immune activation. Maintaining low testosterone levels in resource-limited and/or high pathogen-risk environments may avoid some immunosuppression and suspend energetically-expensive anabolic functions. Augmenting testosterone levels in the presence of fertile and receptive mates, areas of high food resource availability, and low disease risk habitats will function to maximize lifetime reproductive success.

Body mass, depressive symptoms and menopausal status: An examination of the “Jolly Fat” hypothesis

PURPOSE

Estrogens are linked with depression due to their ability to alter the function of the serotonin neural systems. We hypothesize that postmenopausal women should have a higher degree of depressive symptoms than premenopausal women. Further, because estrogen levels in postmenopausal women positively correlate with body fat, we hypothesize that there is an inverse relationship between body fat and depressive symptoms among postmenopausal women.

METHODS

We enrolled 1156 Polish urban women aged 45 to 64 in a cross-sectional study. Depressive symptoms were assessed by the Center for Epidemiologic Studies-Depression Scale (CES-D) scale. Menopausal status and education level was assessed by a standardized questionnaire.

MAIN FINDINGS

Postmenopausal women had higher mean CES-D scores of depressive symptoms than premenopausal women (14.4 versus 13.2 respectively, p = .018). Both among pre- and postmenopausal women, those with higher education had lower scores of depressive symptoms. In addition, in postmenopausal women with lower education an inverse relationship was observed between body mass index (BMI) and depressive symptoms: a higher BMI was associated with a lower score of depressive symptoms (p = .009). Such a relationship was not present among premenopausal women or women who were postmenopausal but better educated.

CONCLUSIONS

This study indicates that menopausal status is related to differences in the degree of occurrence of depressive symptoms. Our results support the "Jolly Fat" hypothesis for postmenopausal women with lower education, namely, a higher BMI is associated with lower score of depressive symptoms.

High ponderal index at birth predicts high estradiol levels in adult women

Inter-individual variation in levels of sex hormones results from differences in genetic, developmental, and environmental factors. We tested a hypothesis that programming of the fetal neuroendocrine axis may predispose some women to produce higher levels of steroid hormones during their menstrual cycles as adults. One hundred forty-five regularly menstruating 24- to 36- year-old women collected daily saliva samples for one menstrual cycle. Data on women's birth weights and birth lengths were obtained from medical records. A positive relationship was observed between ponderal index at birth (an indicator of nutritional status, calculated as birth weight/(birth length)(3)) and levels of estradiol (E2) in menstrual cycles, after controlling for potential confounding factors. Mean E2 was 16.4 pmol/l in the low ponderal index tertile, 17.3 pmol/l in the moderate ponderal index tertile, and 19.6 pmol/l in the high ponderal index tertile (the high ponderal index group had significantly higher E2 than both low and moderate ponderal index groups, P=0.0001). This study shows a positive association between ponderal index recorded for women at birth and levels of E2 measured during their menstrual cycles as adults. This suggests that conditions during fetal life influence adult production of reproductive hormones and may contribute to inter-individual variation in reproductive function. In addition, because large size at birth is one of the factors linked with an increased risk of breast cancer, our findings provide a physiological link for the observed positive relationship between indicators of energetic conditions during fetal growth and breast cancer in women.