Sex differences in body fat parameters from the early reproductive to the postreproductive period of life: a multivariate analysis

Sex diversity has been observed for many body parameters, and special attention has been paid to changes during puberty and menopause. In the present study we performed a multivariate analysis on several body fat parameters to obtain a synthetic overview of sex differences from the early reproductive period to the postreproductive period. The sample study is composed of 373 healthy Italian adults (294 females and 79 males). We have examined the amount of fat (in kilograms, as measured by dual-energy x-ray absorptiometry) in the left arm, left leg, left trunk hemisphere, right arm, right leg, and right trunk hemisphere, waist to hip ratio, and BMI. The sex differentiation from the early reproductive to the postreproductive period of life has been based on differences between the position of male and female centroids on the discriminant functions obtained for various periods of life. The difference between males and females increases suddenly after 20 years, reaching a maximum at 30 years. In the period between 30 and 40 years the difference decreases quickly, and after 40 years the difference is relatively small and remains practically constant. The fact that maximum sex differentiation coincides with age of best reproductive efficiency points to a relationship between the body parameters investigated and hormone production related to human reproduction.     

Gestational and early life influences on infant body composition at 1 year

Excess weight gain during both pre‐ and postnatal life increases risk for obesity in later life. Although a number of gestational and early life contributors to this effect have been identified, there is a dearth of research to examine whether gestational factors and weight gain velocity in infancy exert independent effects on subsequent body composition and fat distribution.

Objective:

To test the hypothesis that birth weight, as a proxy of prenatal weight gain, and rate of weight gain before 6 months would be associated with total and truncal adiposity at 12 months of age.

Design and Methods:

Healthy, term infants (N = 47) were enrolled in the study and rate of weight gain (g/day) was assessed at 0‐3 months, 3‐6 months, and 6‐12 months.

Results:

Total and regional body composition were measured by dual‐energy X‐ray absorptiometry (DXA) at 12 months. Stepwise linear regression modeling indicated that lean mass at 12 months, after adjusting for child length, was predicted by rate of weight gain during each discrete period of infancy (P < 0.05), and by maternal pre‐pregnancy BMI (P < 0.05). Total fat mass at 12 months was predicted by rate of weight gain during each discrete period (P < 0.01), and by older maternal age at delivery (P < 0.05). Trunk fat mass at 12 months, after adjusting for leg fat mass, was predicted by rate of weight gain from 0‐3 months and 3‐6 months (P < 0.05).

Conclusion:

Results suggest that growth during early infancy may be a critical predictor of subsequent body composition and truncal fat distribution.     

Sex differences in growth rates of early life stage Japanese eels Anguilla japonica under experimental conditions

To assess the relationship between growth rate of body mass and sex in the Japanese eel Anguilla japonica in the early life stage; the growth rates of males and females were compared under experimental conditions. The mean growth rate of females was significantly slower than that of males. To assess the relative priority of growth rate and sex, growth was delayed by restricted feeding, resulting in a significantly higher proportion of females in the delayed than in the normal growth group. These findings indicate that the mean growth rate of A. japonica is slower in females than in males in the early life stage around sex determination and differentiation under experimental rearing conditions. Moreover, growth rate probably has priority over sex determination, with slow growth rate increasing the probability of being female.     

Sex differences in the jealousy-evoking nature of a rival's body build

This study among 185 college students showed that potential rivals with a relatively low waist-to-hip ratio (WHR) evoked more jealousy in women than in men. In contrast, rivals with a relatively high shoulder-to-hip ratio (SHR) evoked more jealousy in men than in women, particularly when the rival also had a high WHR. Rivals with a low as opposed to a high WHR were perceived as more socially dominant and attractive in both sexes, and as more physically dominant in the case of men. In addition, rivals of both sexes were perceived as more physically and socially dominant when they had a high SHR, and in the case of men as more attractive. In evaluating the rivals, women indicated that they had paid more attention to the rivals' waist, hips, and legs, and men indicated that they had paid more attention to the rivals' shoulders, chest, and belly. The results provide support for evolutionary psychological hypotheses that men and women pay attention to different bodily features in evaluating the potential threat imposed by a rival.     

Sex differences in body composition of wintering Mallards (Anas platyrhynchos): possible implications for survival and reproductive performance

Capsule Wintering female Mallards have a higher fat load than males which may compensate for their lower body size and ultimately improve their fitness.

Aims To investigate whether sex-related differences in biological processes in winter are associated with differences in body nutrient storage and flight capabilities and, if so, the possible implications for survival and reproductive performance.

Methods We analysed the body composition and the flight parameters of 35 male and 35 female Mallards wintering in western Europe on the Rhine river.

Results Males were 15% heavier and 18% larger than females, but the latter carried 27% more fat per unit body mass. Relative to body lipid mass, body protein mass was 11% lower for females. Wing loading was 7% lower in females and power loading was similar in both sexes.

Conclusions High lipid mass gives females survival capabilities to food shortage similar to males. This helps sustain them through their prebasic moult and breeding success. Heavier muscles in males compensate for their higher wing loading and thus improve pairing success. Wintering and reproductive strategies in Mallard seem to be closely linked through body reserves.     

Sex differences in life expectancy in Canada: immigrant and native-born populations

A growing body of research often indicates that immigrant populations in Western countries enjoy a lower level of mortality in relation to their native-born host populations. In this literature, sex differences in mortality are often reported but substantive analyses of the differences are generally lacking. The present investigation looks at sex differences in life expectancy with specific reference to immigrant and Canadian-born populations in Canada during 1971 and 2001. For these two populations, sex differences in expectation of life at birth are decomposed into cause-of-death components. Immigrants in Canada have a higher life expectancy than their Canadian-born counterparts. In absolute terms, immigrant females enjoy the highest life expectancy. In relative terms, however, immigrant men show a larger longevity advantage, as their expectation of life at birth exceeds that of Canadian-born men by a wider margin than do foreign-born females in relation to Canadian-born females. It is also found that immigrants have a smaller sex differential in life expectancy as compared with the Canadian born. Decomposition analysis shows this is a function of immigrants having smaller sex differences in death rates from heart disease and cancer. Factors thought to underlie these differentials between immigrants and the Canadian born are discussed and suggestions for further research are given.     

Sex differences in the chemical composition of uropygial gland waxes in domestic ducks

Sexual differences in the chemical composition of the uropygial gland waxes in domestic ducks have been detected before the nesting period. 3-Hydroxy fatty acids containing diester waxes and significant differences in the composition of the fatty acid and alcohol moieties of the monoester waxes occur during February–June only in the female preen wax. Males as well as ducklings, however, show constant wax patterns. Moreover, no significant influence on wax composition of testosterone or estradiol, respectively in male or female ducklings could be verified.     

Interspecies differences in the empty body chemical composition of domestic animals

Domestication of animals has resulted in phenotypic changes by means of natural and human-directed selection. Body composition is important for farm animals because it reflects the status of energy reserves. Thus, there is the possibility that farm animals as providers of food have been more affected by human-directed selection for body composition than laboratory animals. In this study, an analysis was conducted to determine what similarities and differences in body composition occur between farm and laboratory animals using literature data obtained from seven comparative slaughter studies (n = 136 observations). Farm animals from four species (cattle, goats, pigs and sheep) were all castrated males, whereas laboratory animals from three species (dogs, mice and rats) comprised males and/or females. All animals were fed ad libitum. The allometric equation, Y = aX^b, was used to determine the influence of species on the accretion rates of chemical components (Y, kg) relative to the growth of the empty body, fat-free empty body or protein weights (X, kg). There were differences between farm and laboratory animals in terms of the allometric growth coefficients for chemical components relative to the empty BW and fat-free empty BW (P < 0.01); farm animals had more rapid accretion rates of fat (P < 0.01) but laboratory animals had more rapid accretion rates of protein, water and ash (P < 0.01). In contrast, there was no difference in terms of the allometric growth coefficients for protein and water within farm animals (P > 0.2). The allometric growth coefficients for ash weight relative to protein weight for six species except sheep were not different from a value of 1 (P > 0.1), whereas that of sheep was smaller than 1 (P < 0.01). When compared at the same fat content of the empty body, the rate of change in water content (%) per unit change in fat content (%) was not different (P > 0.05) across farm animal species and similar ash-to-protein ratios were obtained except for dogs. The fraction of empty body energy gain retained as fat increased in a curvilinear manner, and there was little variation among farm animals at the same fat content of the empty body. These findings may provide the opportunity to develop a general model to predict empty body composition across farm animal species. In contrast, there were considerable differences of chemical body composition between farm and laboratory animals.     

Sex and genetic differences in hair color changes during early childhood.

Hair color was assessed routinely from three months to six years for children participating in a longitudinal study of twins: 169 female twin pairs, 161 male pairs, and 60 opposite-sex pairs. Age trends, established by sampling only one number of every pair, showed marked changes in hair color for both sexes, but there was a consistent excess of light-haired males and dark-haired females. Within-pair concordance rates were calculated for same-sex pairs whose zygosity had been determined independently through bloodtyping. A high rate of concordance was found for MZ twins at every age in spite of the general change in hair color, indicating a strong genetic influence in the timing of color changes. The results are discussed in terms of accelerated maturation of females, and the need for genetic models of the inheritance of hair color which are age- and sex-specific.     

Sex differences in the lipolytic activity of Galleria mellonella fat body

The sexual differences in the intensity of production and release of free fatty acids (FFA) as well as the differences in the absolute amount of FFA produced and released from the fat body are most conspicuous at the sixth day after the larval-pupal ecdysis. Furthermore, it is demonstrated that a significant difference exists in the lipolytic activity of the fat body between the two sexes.     

Sex differences in recombination

One of the stronger empirical generalizations to emerge from the study of genetic systems is that achiasmate meiosis, which has evolved 25–30 times, is always restricted to the heterogametic sex in dioecious species, usually the male. Here we collate data on quantitative sex differences in chiasma frequency from 54 species (4 hermaphroditic flatworms, 18 dioecious insects and vertebrates and 32 hermaphroditic plants) to test whether similar trends hold. Though significant sex differences have been observed within many species, only the Liliaceae show a significant sexual dimorphism in chiasma frequency across species, with more crossing over in embryo mother cells than in pollen mother cells; chiasma frequencies are unrelated to sex and gamety in all other higher taxa studied. Further, the magnitude of sexual dimorphism, independent of sign, does not differ among the three main ecological groups (dioecious animals, plants, and hermaphroditic animals), contrary to what would be expected if it reflected sex-specific selection on recombination. These results indicate that the strong trends for achiasmate meiosis do not apply to quantitative sex differences in recombination, and contradict theories of sex-specific costs and benefits. An alternative hypothesis suggests that sex differences may be more-or-less neutral, selection determining only the mean rate of recombination. While male and female chiasma frequencies are more similar than would be expected under complete neutrality, a less absolute form of the hypothesis is more difficult to falsify. In female mice the sex bivalent has more chiasmata for its length than the autosomes, perhaps compensating for the absence of recombination in males. Finally, we observe that chiasma frequencies in males and females are positively correlated across species, validating the use of only one sex in comparative studies of recombination.     

Sex differences in senescence: the role of intra-sexual competition in early adulthood

Males and females frequently differ in their rates of ageing, but the origins of these differences are poorly understood. Sex differences in senescence have been hypothesized to arise, because investment in intra-sexual reproductive competition entails costs to somatic maintenance, leaving the sex that experiences stronger reproductive competition showing higher rates of senescence. However, evidence that sex differences in senescence are attributable to downstream effects of the intensity of intra-sexual reproductive competition experienced during the lifetime remains elusive. Here, we show using a 35 year study of wild European badgers (Meles meles), that (i) males show higher body mass senescence rates than females and (ii) this sex difference is largely attributable to sex-specific downstream effects of the intensity of intra-sexual competition experienced during early adulthood. Our findings provide rare support for the view that somatic maintenance costs arising from intra-sexual competition can cause both individual variation and sex differences in senescence.     

Sex differences in total body water in adolescent rhesus macaques estimated by ethanol dilution

Abstract: Non‐human primates are widely used in research, yet relatively few studies have addressed potential pharmacokinetic differences between males and females. The present study examined the relationship between total body water, sex, age, and weight in the rhesus macaque (Macaca mulatta). Ethanol‐naïve, adolescent rhesus macaques (n = 119) were administered ethanol (males, 2.1 g/kg; females, 2.0 g/kg) intravenously, and blood samples for blood ethanol concentration obtained at 5, 10, and 60 minutes following the end of the infusion. Non‐linear regression was used to compare and contrast a series of pharmacokinetic models examining the relationship between weight, sex, age, V_d and zero‐order elimination rate. V_d (mean ± SEM) for male rhesus was 0.771 ± 0.008 l/kg and for females was 0.730 ± 0.008 l/kg, different at P < 0.00001. There were no sex differences in the rate of zero‐order ethanol elimination, estimated to be 0.0032 ± 0.0004 g/kg/minute. The data reported here may be useful in designing and interpreting pharmacokinetic studies using rhesus monkeys.