Here’s the tricky thing about using sweat as a barometer for health: “A lot of it comes down to biological variation,” says Dr. Craig Crandall, a professor of internal medicine at the University of Texas Southwestern Medical Center.
Crandall says if you examined two people—same height, sex and build—one might produce twice the volume of perspiration as the other. “It could just be one person has more sweat glands,” he explains. “Everybody’s baseline is different, so it’s hard to say what amount of sweat is ‘healthy’.”
Still, patterns emerge when you look at big groups of people.
Fit people not only perspire more, but they also start sweating sooner during exercise, says study coauthor Dr. Yoshimitsu Inoue of Osaka International University.