Greater male variability in daily energy expenditure develops through puberty.

There is considerably greater variation in metabolic rates between men than between women, in terms of basal, activity and total (daily) energy expenditure (EE). One possible explanation is that EE is associated with male sexual characteristics (which are known to vary more than other traits) such as musculature and athletic capacity. Such traits might be predicted to be most prominent during periods of adolescence and young adulthood, when sexual behaviour develops and peaks. We tested this hypothesis on a large dataset by comparing the amount of male variation and female variation in total EE, activity EE and basal EE, at different life stages, along with several morphological traits: height, fat free mass and fat mass. Total EE, and to some degree also activity EE, exhibit considerable greater male variation (GMV) in young adults, and then a decreasing GMV in progressively older individuals. Arguably, basal EE, and also morphometrics, do not exhibit this pattern. These findings suggest that single male sexual characteristics may not exhibit peak GMV in young adulthood, however total and perhaps also activity EE, associated with many morphological and physiological traits combined, do exhibit GMV most prominently during the reproductive life stages.

Variability in energy expenditure is much greater in males than females.

In mammals, trait variation is often reported to be greater among males than females. However, to date, mainly only morphological traits have been studied. Energy expenditure represents the metabolic costs of multiple physical, physiological, and behavioral traits. Energy expenditure could exhibit particularly high greater male variation through a cumulative effect if those traits mostly exhibit greater male variation, or a lack of greater male variation if many of them do not. Sex differences in energy expenditure variation have been little explored. We analyzed a large database on energy expenditure in adult humans (1494 males and 3108 females) to investigate whether humans have evolved sex differences in the degree of interindividual variation in energy expenditure. We found that, even when statistically comparing males and females of the same age, height, and body composition, there is much more variation in total, activity, and basal energy expenditure among males. However, with aging, variation in total energy expenditure decreases, and because this happens more rapidly in males, the magnitude of greater male variation, though still large, is attenuated in older age groups. Considerably greater male variation in both total and activity energy expenditure could be explained by greater male variation in levels of daily activity. The considerably greater male variation in basal energy expenditure is remarkable and may be explained, at least in part, by greater male variation in the size of energy-demanding organs. If energy expenditure is a trait that is of indirect interest to females when choosing a sexual partner, this would suggest that energy expenditure is under sexual selection. However, we present a novel energetics model demonstrating that it is also possible that females have been under stabilizing selection pressure for an intermediate basal energy expenditure to maximize energy available for reproduction.

Association between overweight and anemia in Moroccan adolescents: a cross-sectional study.

Introduction: obesity and anemia remain global public health problems, having major negative effects on human health. We aimed to estimate the prevalence of anemia and investigate its association with overweight/obesity and excess body fat among Moroccan adolescents. Methods: a total of 292 adolescents aged 11-17 years were recruited. Body mass index (BMI) and waist circumference (WC) were determined using standardized equipment. Body fat mass was measured by bioelectrical impedance analysis. Hemoglobin concentration was measured by the HemoCue method. Results: the overall prevalence of anemia was 13.7%. Anemia was more common among overweight/obese participants (15.2%) compared to non-overweight participants (12.8%). Overweight/obese boys were more likely to experience anemia than their non-overweight peers (odds ratio (OR): 1.49; 95% confidence interval (95%CI): 0.51-4.41). Similarly, anemia likelihood was higher among individuals having excess body fat than those who do not have excess body fat, particularly among girls (OR: 1.64; 95%CI: 0.69-3.87). Excess body fat was also significantly associated with lower hemoglobin concentration in both the total sample and girls (P=0.014, and P=0.041, respectively). Overall, increased BMI, WC, fat mass, and percent body fat were associated with reduced hemoglobin concentrations. There was a significant negative correlation between hemoglobin concentration and BMI among anemic girls (P=0.023). Conclusion: elevated BMI and body fat level were associated with lower hemoglobin concentrations and anemia. Further studies are needed to delineate the basis of such associations, and if these findings are confirmed, the guidelines for screening for anemia may need to be modified to include overweight/obesity as a risk factor.

The opposing effects of acute inflammation and iron deficiency anemia on serum hepcidin and iron absorption in young women.

Hepatic hepcidin synthesis is stimulated by inflammation but inhibited during iron deficiency anemia (IDA). In humans, the relative strength of these opposing signals on serum hepcidin and the net effect on iron absorption and systemic iron recycling is uncertain. In this prospective, 45-day study, in young women (n=46; age 18-49 years) with or without IDA, we compared iron and inflammation markers, serum hepcidin and erythrocyte iron incorporation from 57Fe-labeled test meals, before and 8, 24 and 36 hours (h) after influenza/DPT vaccination as an acute inflammatory stimulus. Compared to baseline, at 24-36 h after vaccination: 1) interleukin-6 increased 2-3-fold in both groups (P<0.001); 2) serum hepcidin increased >2-fold in the non-anemic group (P<0.001), but did not significantly change in the IDA group; 3) serum iron decreased in the non-anemic group (P<0.05) but did not change in the IDA group; and 4) erythrocyte iron incorporation did not change in either of the two groups, but was approximately 2-fold higher in the IDA group both before and after vaccination (P<0.001). In this study, mild acute inflammation did not increase serum hepcidin in women with IDA, suggesting low iron status and erythropoietic drive offset the inflammatory stimulus on hepcidin expression. In non-anemic women, inflammation increased serum hepcidin and produced mild hypoferremia, but did not reduce dietary iron absorption, suggesting iron-recycling macrophages are more sensitive than the enterocyte to high serum hepcidin during inflammation. The study was registered as a prospective observational trial at clinicaltrials.gov identifier: 02175888 The study was funded by the International Atomic Energy Agency.