The common cliché goes that women freeze at higher temperatures than men. Some surveys also suggest this. But a new study now contradicts this. Accordingly, the female body apparently only counteracts cooling at lower ambient temperatures and begins to generate heat later. Why is that? And how does the comfortable temperature differ for men and women?
At typical room temperatures, such as those found in offices, women tend to freeze more quickly than men. At least that’s what various surveys suggest. But whether this is true and why it is is unclear. How the female body reacts to low temperatures has hardly been studied so far.
How does our body prevent itself from cooling down?
A team led by Robert Brychta from the British National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) in Bethesda has now compared the heat regulation of women and men. To do this, they first analyzed various metabolic parameters of 16 women and 12 men: total energy expenditure, the proportion of brown fat tissue in the body, and skin and core temperature. They also asked the test subjects at what temperatures they felt comfortable and checked under what circumstances they shivered. The room temperature in the experiments ranged from 17 to 31 degrees Celsius. The test subjects were all young and had a thin build. From the measured parameters, Brychta and his colleagues then calculated the room temperature at which the test subjects objectively freeze and their bodies counteract cooling. Because below this threshold, human bodies activate mechanisms to conserve heat and expend measurably more energy to maintain constant body temperature.
The surprising result: In women, this cold-induced thermogenesis begins on average at lower room temperatures than in men, not at higher ones. In the experiments, their critical temperature averaged 21.9 degrees Celsius, while that of men was 22.9 degrees. So although women may subjectively freeze more quickly in everyday life, their objectively observed thermoregulation suggests the opposite. The researchers attribute this “arctic” shift in large part to the higher body fat percentage in women, which insulates their bodies better than those of men with the same BMI. This is consistent with observations from another study, according to which the critical temperature is lower in overweight men with a higher body fat percentage than in men of normal weight.
From their observations, the team concludes that the insulating effect of body fat outweighs other factors in thermoregulation. The fact that women are smaller on average and therefore have lower energy expenditure and lower heat production than men seems to be of surprisingly little importance, as Brychta and his colleagues report.
What determines the regulation of body temperature
Overall, the study suggests that various physical factors come into play in the heat regulation of the human body. The decisive factors include body size, stature and the amount of muscle and fat. These parameters are at least partially associated with gender. However, the researchers found no gender-specific differences in other factors that contribute to thermoregulation, such as the activity of the muscles when trembling or brown adipose tissue. The subjective feel-good temperature also did not differ between the male and female test subjects – contrary to common assumption. Follow-up studies with a larger number of test subjects must now examine the findings. Only then can it be said with certainty whether women freeze sooner or later than men.
Source: Robert Brychta (National Institute of Diabetes and Digestive and Kidney Diseases) et al., Proceedings of the National Academy of Sciences (PNAS), doi: 10.1073/pnas.2311116121