Do men really sweat more than women?

Men are generally taller than women, but we do not define gender by height. Similarly, our latest research shows that we can’t define men and women based on their tendency to sweat (though some parents and partners may suggest otherwise).

When we examined men and women during exercise in heated and arid conditions, sex differences in responses to heat loss (skin blood flow and sweating) could be explained almost exclusively by individual differences in body size and shape.

These results debunk the common saying that “men sweat and women glow.”

How objects and bodies lose heat

Heat loss from any object is dictated by its surface area to mass ratio, described by the term “specific surface area.” Scorching objects with larger specific surface areas nippy faster than those with smaller specific surface areas. Doubling the radius (size) of a sphere increases its surface area fourfold but its mass eightfold: this is known as “isometric growth.” Isometrically larger objects do not lose heat as easily.

Shape (morphology) also has a forceful influence on heat loss, so a gaunt cuboid loses heat much faster than a sphere of the same composition and mass. In the previous article, we explained that heat is no more likely to be lost from the head than from other parts of the body.

Unlike geometric objects, animals do not grow isometrically; we retain a recognizable shape, but our proportions change (a phenomenon called “allometric growth”). This is most noticeable in children, who have proportionally larger heads and shorter limbs than adults.

However, if you double your weight by building muscle and gaining weight (without changing your height), this will not double your skin surface area. This weight change increases your skin surface area only about 30%which translates into reduced specific surface area and less heat loss through these physical mechanisms. The larger a person is, the smaller their specific surface area and the less effective these mechanisms become. This is where physiological heat loss mechanisms, particularly sweating, come into play, preventing unwanted heat gain.

Sweating and evaporative cooling

Because humans have evolved in the heat of Africawe have acquired the ability to transport heat from deep within our bodies to the surface of our skin in order to dissipate it via blood flow through the skin. Similarly, we have acquired an evaporative cooling mechanism that can operate when the air is warmer than the skin: sweating. These physiological responses allow us to manage body heat and are activated when physical heat loss becomes insufficient.

To investigate the influence of body shape and gender on these two physiological responses to manage body heat, we studied men and women (60 university students) of very different but overlapping body sizes. The subjects had very similar exercise habits, endurance, and body fat.

For each participant, we calculated a target exercise intensity directly related to their skin surface area. This resulted in comparable increases in core body temperature across all participants and equivalent heat loss requirements. To our knowledge, this was the first study to achieve such results in a morphologically diverse sample of men and women. Previous investigators clearly did not fully appreciate these crucial criteria of experimental design, leading to experiments that perpetuated the myth that all men sweat more than women.

Our analyses showed that differences in cutaneous blood flow and sweating in men and women depend not on gender but on body morphology.

By answering our questions, we showed that the lyrics of the songs “Down Under” (Men at Work) require modification.

Are you from the antipodes?

Where women shine and men plunder?

Even though we come from the land down under, and some men are still allowed to plunder, unfortunately, women don’t glow. They sweat just like men and for the same reason: to lower their body temperature.

Three different types of sweat

To consider the relationship between sweat and body odor, we need to look at it a little more broadly.

The ubiquitous sweat glands that humans have for evaporative cooling are known as “eccrine” glands. However, we all have two other types of glands in our skin: “apocrine” and “apoeccrine” glands.

While eccrine glands are distributed throughout the body, apocrine and apoeccrine glands have a confined surface area and are located primarily in areas where longer and sometimes curlier hair grows in adults (whether or not we remove that hair).

Apocrine glands are located next to hair follicles, where they secrete a milky, oily fluid. Apocrine glands, which appear to develop after puberty, appear to be the dominant glands in the armpits. They secrete a watery fluid, similar to eccrine glands.

The odor we sometimes sense around sweaty people or their clothes comes mainly from the secretions of the apocrine and apoeccrine glands. These secretions are initially inodorous, but the action of bacteria on this fluid causes stinky men and stinky women.