A study found that men's height and weight may be significantly more sensitive to environmental conditions than women's, with males experiencing more than double the physical development gains as living conditions improve.
In the study, published in Biology Letters, investigators, led by David Giofrè from the University of Genoa, analyzed World Health Organization (WHO) data from 62 countries and found that improvements in national living standards, as measured by the Human Development Index (HDI), corresponded to greater increases in male height and weight compared with their female counterparts.
"Each 0.2 increase in HDI was associated with an average height increase of approximately 1.68 cm for females and 4.03 cm for males," the study authors reported. Similarly, weight gains showed marked sex differences, with men gaining 6.48 kg compared with women's 2.70 kg for each 0.2 HDI increase.
The researchers suggested that sexual size dimorphism (SSD) in height may serve as a particularly sensitive indicator of population health. When analyzing UK data spanning births from 1900 to 1958, the investigators found that male height increased by 0.69 cm per 5-year interval, whereas female height increased by 0.25 cm. Additionally, in the UK cohort, variation in male height decreased more over time compared with female height, suggesting that improved conditions may lead to more consistent male physical development. However, this pattern was not observed in the cross-national WHO data.
The findings align with evolutionary biology theories that suggest sexually selected traits in males are more vulnerable to developmental stressors such as malnutrition and infectious disease. The investigators noted that "men's height should be especially sensitive to disruption by infectious disease and nutritional shortfalls during development."
The study also examined the impact of income inequality on physical development using the World Bank’s Gini index. The results showed that each 1 unit increase in inequality was associated with height decreases of 0.31 cm for males compared with 0.14 cm for females. Similarly, greater income inequality was linked to larger weight reductions in men compared with women, further supporting the idea that male physical development is particularly sensitive to environmental conditions.
In nations with improved living conditions, not only did absolute measurements increase more dramatically for men, but variation in height among males decreased more significantly compared with females in the UK data set. This suggested that optimal conditions allow for more uniform male physical development.
The study combined data from multiple sources, including WHO surveys of 135,645 participants across 62 countries, Wikipedia height data from over 130 countries, and historical UK height data covering 49,180 adults born between 1900 and 1958.
Although the investigators recognized the correlational nature of their findings, they highlighted the necessity of longitudinal studies that track cohorts with different levels of early-life stress exposure to better understand the relationships.
The authors declared having no competing interests.
