Are you more cautious than others? This week, France is affected by an episode of exceptional coolness, in the middle of a fairly mild winter. While some tremble under their scarves, others walk the streets in light clothing.
A difference in the sensation of cold that can be explained on a biological and physiological level, as deciphered for BFMTV.com by Cédric Moro, research director at Inserm and doctor in pathophysiology.
“There are different factors that explain the differences in the sensations or perception of cold.”
The first determining element: sex. Yes, women are more cautious than men, to some extent. Their muscle mass is, in general, lower than that of men, but it plays a predominant role in heat production.
Respectively, muscles represent 28% and 35% of the compositions. This does not prevent women from being more muscular than men, or quite the opposite.
A question of hormones
Another difference linked to sex, on the hormonal side. Dimitra Gkika, professor of physiology at the University of Lille and member of the Canther Laboratory, studied the role of testosterone in animals:
“Testosterone will inhibit the cold receptor TRPM8. It normally detects the drop in temperature at the level of sensory neurons in the skin. Testosterone can inhibit the activity of this receptor by up to 70%” (Gkika et al 2022 Faseb Journal).
This phenomenon explains both the difference between both sexes and between younger and older men. Once testosterone decreases in the body, 30 to 50% more chills may occur.
“The level of testosterone in men increases during puberty with a peak at age 20. It begins to decrease at age 30 according to the profiles, but we can observe a fairly significant decrease after age 50,” specifies the Lille researcher. .
“brown fat”
Continuing with the theme of age, muscle mass comes into play again. As Cédric Moro points out, from the age of 30, it decreases between 3 and 5% annually among individuals. However, the loss of this “crucial site for heat production” causes a more intense sensation of cold.
Age also means the disappearance of our “brown fat”, the adipose tissue that burns calories to produce heat. A fat that is not present in overweight and obese people, who have more “white fat.”
“This ‘white fat’, however, plays an insulating role in overweight people. It acts a bit like several layers of clothing,” summarizes the Inserm researcher.
From the compilation of all these factors, different ideal temperatures arise according to each individual. An average man between 20 and 30 years old, of normal weight, experiences “thermoneutrality” between 22 and 24°C. In a woman, it is 24-25°C. Hence the difficulty of agreeing on the ideal temperature in offices, for example.
Evolution and hairiness
A final element may intervene, evolution and genetic specificities. For example, the Inuit have been found to have higher levels of white and brown fat. Potentially a response to living in a hostile environment due to sub-zero temperatures.
To a lesser extent, Finns appear to be less cold, possibly due to their exposure “to significant thermal stress,” according to Cédric Moro. Therefore, their threshold for recognizing cold would be higher.
However, there is one trait that seems laughable: hairiness. This vestige of evolution now plays a “marginal” role in human heat loss and, therefore, in the sensation of cold.
Source: BFM TV
