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Cambridge University Science Magazine
The study, published in Proceedings of the National Academy of Sciences [1] (PNAS), extends the concept of developmental plasticity - i.e. how the body responds early in life to things like nutrition and stress, and the risk of diseases like heart attack, diabetes and hypertension - to the realm of sex differences and male biology. It suggests rapid weight gain in the period of birth to six months (B6M) predicts earlier puberty for boys. The study was conducted among a group of 770 Filipino males (aged 20.5 to 22.5 years) followed since birth, by birth weight and weight velocities. Infants who were breastfed experienced less diarrhea, lived in wealthier households with better hygiene, and grew faster after B6M. Males with rapid B6M growth reached puberty earlier and, as young adults, had higher testosterone levels, were taller, more muscular, and had higher grip strength. They also had sex earlier and more lifetime sex partners.

These results are explained by fact that male infants in the first six months of life produce testosterone at approximately the same level as an adult male. Testosterone is known to increase muscle mass and puts a person on a higher growth trajectory to be taller. As testosterone is very high from B6M for healthier infant males, it helps shape the differences between males and females and the magnitude of the difference appears to be the result of nutrition during the early month's of a male infants life.

Written by Nitika Somani


  1. Christopher W. Kuzawa et al., “Rapid weight gain after birth predicts life history and reproductive strategy in Filipino males,” Proceedings of the National Academy of Sciences 107, no. 39 (2010): 16800 -16805.