To stay healthy, it is best to exercise at least 2.5 to 5 hours every week, as recommended by the World Health Organization (WHO). Every minute of high intensity exercise – walking, brisk cycling, basketball – can be counted double.
In its recommendation, the WHO makes no distinction between men and women (unless they are pregnant or have just given birth). However, the health benefits of regular exercise differ according to gender. This is shown by a study that has just been published in the journal Journal of the American College of Cardiology.
That study followed more than 400,000 Americans between the ages of 27 and 61 in the period between 1997 and 2019. Nearly 40,000 of them died during that period.
Compared to peers who never exercise, men who exercise for five hours at a moderate intensity or almost two hours of intensive exercise every week were 19 percent less likely to die in the same period. Women achieved the same benefit by exercising for 140 minutes of moderate intensity (less than 2.5 hours) or one hour of intensive exercise. If women exercise even more, they can reduce their risk by 24 percent.
Even if men exercise more, the average man never achieved as great a health gain as a woman. After five hours of moderate intensity exercise per week, the health gains for men and women reach a plateau: more exercise does not further reduce the risk of premature death.
The researchers observed a similar pattern for strength training. Men who did muscle-strengthening exercises three times a week were 14 percent less likely to die. Women already achieved this benefit from one training session per week. If they also trained three times a week, the reduction in mortality risk was twice as high as for men.
In such observational studies it is virtually impossible to prove a causal relationship. There is a risk that the results will be contaminated because the opposite also applies: it is precisely the people who are less likely to die who exercise more. To rule this out, the researchers always compare people with a similar health condition, age and socio-economic background. Sick people were not included in the study.
A good study, says exercise and sports scientist Sofie Compernolle (UGent). Although she also sees limitations. “For example, dietary habits are not taken into account. It is possible that women who exercise a lot in their spare time also have a healthier diet.” She also points out that the study only takes into account exercise during leisure time, while people also exercise during (household) work or during work trips.
“The main shortcoming is that they measure physical activity with questionnaires,” says Compernolle. “That is a common approach in large-scale studies. But questionnaires are prone to bias.” People do not always accurately report how much they exercise. Although, based on smaller checks, the researchers are confident that the questionnaires are sufficiently reliable.
Half an hour is enough
The researchers also have an idea why women benefit more from exercise. Men generally have a larger heart, more lung capacity and have more muscle fibers. The same training is more difficult for women and produces more health benefits.
“On average, women exercise less often than men,” says cardiologist and co-author of the study Susan Cheng in a press release. “Hopefully our research results will inspire women to exercise more.” They do not have to make every effort immediately. “Even a limited amount of regular exercise can be very beneficial. This is especially the case for women,” says Cheng. “Even if you exercise intensively for ‘only’ 20 to 30 minutes: if you do that a few times a week, it will yield much more than you would think.”
