Women’s Menarche – It’s All About The Thigh Fat
With the help of cross-sectional data from the third National Health and Nutrition Examination Survey (NHANES III) for females aged 10–14, researchers William Lassek and Steven Gaulin, University of California at Santa Barbara, found that menarche was more closely related to fat distribution than to skeletal maturity.
The researchers found that each unit increase in hip circumference it increased odds by 24% of menache occurring while increases in triceps skinfolds and waist circumference lowered odds by 7 and 9% respectively. The results showed that despite having relatively low levels of fat overall, menache was associated with more fat deposits on the gluteofemeral area (lower body fat). Fat deposits in the hips and buttock was a key area signaling onset of menache. Young girls with lower waist-hip-ratios also tend to have an increased odds of menache.
“Fat distribution may be relevant because gluteofemoral fat may provide neurodevelopmentally important fatty acid reserves,” say the researchers in their paper.
Rather than total fat, which was not a significant predictor of menarche, it is instead the distribution of fat that decides menarche.
The researchers suggest that gluteofemoral fat is a key generator of the hormone leptin which mediates the process. Previous evidence has suggested that gluteofemoral fat produces more leptin than upper-body-fat.
Overall, it is these fat reserves which near about 16 kg added between childhood and puberty, which is likely to be critically important in storing resources needed to bear out pregnancy successfully.
Nevertheless, this research suggests that we are programmed to view these distributions of fat as more healthy, and sexually attractive as they signal reproductive maturity. High amounts of upper body fat, rather than lower body fat, and a high, waist-hip-ratio, is unlikely to be found to be attractive on women at any age.
Closely mimicking the reproductive onset of menache is something most women, and most beauty ideals strive for, and for good reason. It signals onset of menache and thus signals a long reproductive life. The research suggests that it is women whom maintain these signals including higher lower than upper body fat and a low hip-waist-ratio above all others, as well as a lower overall body fat percentage, that will be more successful in drawing attention from male suitors.
Lessek, William D. and Steven J.C. Gaulin. Brief Communication: Menarche is Related to Fat Distribution. American Journal of Physical Anthropology. 2007. 133:1147-1151.