Friday, January 24, 2025 - Human size has increased over the past century thanks to better health and nutrition, but this change has not occurred equally among men and women, a new study shows.
Men have grown taller and heavier at more
than twice the rate of women, according to the study published this week
in the journal, Biology Letters.
The researchers from Italy, the United
States and the United Kingdom analyzed data provided in 2003 by the World
Health Organization on the height and weight of more than 100,000 people across
69 countries. The study authors also used data from the Human Development Index
(HDI), which measures national levels of human well-being.
The team found that each 0.2 increase in
the HDI saw an increase in height of approximately 1.68 centimeters (0.66
inches) for women and 4.03 centimeters (1.59 inches) for men, as well as an
average weight gain of 2.70 kilograms (5.95 pounds) for women and 6.48
kilograms (14.29 pounds) for men.
The trend was also confirmed by assessing
data from the World Bank’s Gini Index, which measures national levels of income
inequality, for 58 countries between 2000 and 2006.
Higher inequality was associated with
decreases in height and weight. Each unit increase in Gini was associated with
an average reduction in height of approximately 0.14 centimeters in women and
0.31 centimeters in men, and an average weight decrease of approximately 0.13
kilograms for women and 0.39 kilograms for men, according to the study.
While it could be thought that more
developed countries could also simply have ethnic populations that are
genetically taller, “we think that isn’t the case,” said study coauthor and
environmental physiologist Lewis Halsey, a professor at the University of
Roehampton who leads the Roehampton University Behaviour and Energetics Lab in
London.
This is because the researchers found a
similar trend when looking at a compilation of adult height data from just one
country: the UK.
By analyzing the heights of 49,180 men and
women between the ages of 23 and 26 from several UK studies published between
1905 and 1958, they found that women’s average height increased by 0.25
centimeters every five years, while that of men increased by 0.69 centimeters.
“This is one of the first studies to make a
connection between the evolution of humankind as driven by sexual selection in
combination with the effects of environment on ultimately our phenotype, so how
we ultimately present ourselves, how we ultimately look characteristically,”
Halsey told CNN on Wednesday.
Halsey believes the difference in the rate
at which men and women are getting taller down to sexual selection. In the
past, taller, heavier men would tend to be stronger, enabling them to
outcompete other men, gaining more access to women and passing on their tall
genes, he said.
However, even today, “women tend to prefer taller men,” he said, while “in
contrast, women’s height isn’t so important. So, to put it simply, men don’t
tend to say, ‘Oh, I only like tall women.’”
“It is (a) nice cross-country study that
basically confirms (an) already well-known rule about the sex differences in
‘ecosensitivity,’” professor Bogusław Pawłowski, the head of the Department of
Human Biology at the University of Wrocław in Poland, who was not involved in
the study, told CNN Wednesday via email.
“As (the) ecological or economical
situation improves and there is better access to resources, males gain more
biological benefits than females. It is exactly opposite when the resources are
scarce (males ‘suffer’ more than females).”
The “taller-male norm is something that
occurs in Western countries (but also in many countries in Asia),” Pawłowski
said. “It means that in these populations (a) man’s height is an important
aspect of a man’s attractiveness on the human mate market.”
The researchers found that the variation in
height among individuals of the same sex was lower in countries with better
living conditions. And, as seen in the UK, within the population of an
individual country, men’s height differences were smaller than women’s as living conditions improved over time.
This is
because men, being bigger than women, “require more energy, they develop for
longer” and, especially having more muscle, their tissues are “metabolically a
bit more active,” Halsey said.
This means
that for me to grow, “it takes longer and it’s more expensive, but that makes
the male body more vulnerable to perturbations, to problems, to influences by
the environment,” such as disease, he added.
So, when
there is a stressful environment with more disease burden, men’s size is a lot
more affected than women’s, he said.
Because
men’s size is more sensitive to living conditions than women’s, the study
authors concluded that men’s height and the differences in height between the
sexes “may be especially useful biomarkers for tracking population changes in
health.”
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