An international team of researchers from the U.S. and China showed that women who exercise regularly have a significantly lower risk of an early death or a fatal cardiovascular event than men who do the same. On top of that, the advantage holds true even when women put in less effort.

The observational study, which analyzed the exercise habits of more than 400,000 U.S. adults, found that compared to being inactive, engaging in regular physical activity lowered women’s mortality risk by 24%. Men saw a 15% reduction in risk.

Women who worked out also had a 36% reduced risk of a fatal cardiovascular event, such as a stroke or heart attack, than their inactive peers. Among men, those who were physically active showed a 14% reduced risk.

Less is more for women’s fitness

The current Physical Activity Guidelines for Americans, developed by the Department of Health and Human Services, recommend at least 150-300 minutes of moderately intense aerobics plus two days of muscle-strengthening activities per week. That these guidelines apply to all adults—regardless of sex—puzzles Dr. Martha Gulati, a coauthor of the study and director of preventive cardiology in the Smidt Heart Institute at Cedars-Sinai Medical Center in Los Angeles.

“Why would it be the same for women versus men?” Gulati, who is also the associate director of the Barbra Streisand Women’s Heart Center at Cedars-Sinai, tells Fortune. “We know women are not small men; we know that there’s physiologic differences. Is the same dose of exercise actually required?”

In addition, Gulati and her colleagues sought to address the well-documented physical activity gap between the sexes.

“We know for young children, girls do less activity than [boys],” she says. “We know that once they’re young adults, we immediately see again this persistent gap. Men do more than women.”

This divide played out in the study too: 43% of male participants engaged in regular aerobic activity, compared to 33% of females. About 28% of men did regular muscle-strengthening activities, versus 20% of women. Men also did both types of exercise more frequently.

While Gulati encourages everyone to find a fitness regimen that fits into their lifestyle, she hopes her team’s findings that women may benefit from a less-is-more approach to exercise will inspire more women to get active.

Male vs. female survival benefits of exercise

Reduced mortality risk from weekly moderate-to-vigorous aerobic activity eventually plateaued for both sexes. But men had to exercise more than twice as long as women to realize the same results, the study found.

It took about 300 minutes, or five hours, per week for men to achieve a maximum 18% lower mortality risk than their inactive peers. Women only had to complete 140 minutes, less than 2 ½ hours, to get the same benefit. Women topped out at a 24% lower mortality risk than their inactive peers at 300 minutes per week.

Researchers observed similar sex differences concerning moderate and vigorous aerobics individually:

• Moderate intensity
  • Men: 20% lower risk at 90 minutes/week
  • Women: 20% lower risk at 50 minutes/week
    • Maximum 24% lower risk at 97 minutes/week
• Vigorous intensity
  • Men: 19% lower risk at 110 minutes/week
  • Women: 19% lower risk at 57 minutes/week
    • Maximum 24% lower risk at 120 minutes/week

“Women got more bang for their buck,” Gulati says.

These findings aren’t meant to suggest fitness enthusiasts shouldn’t work out more than 300 minutes a week, she stresses, only that they likely wouldn’t reap extra survival benefits. Further research is needed to determine whether additional exercise may positively impact other health indicators.

Sex differences in exercise capacity

As with aerobic activity, women had a greater reduction in risk of premature death when it came to regular muscle-strengthening activity. Women saw a 19% lower risk than their inactive peers, while men saw an 11% lower risk.

However, men had an optimum mortality benefit—14% lower risk relative to inactivity—when they did muscle-strengthening activity three times a week. Women showed equal or greater benefit when engaging in such activity just once a week.

So, why did men and women in this study achieve such different results? Gulati and her team cite males’ “measurably greater exercise capacity” across all ages as one possible explanation. They highlighted these attributes of the male form:

• Proportionately larger hearts
• Wider lung airways
• Greater lung diffusion capacity
• Larger muscle fibers
• 38% more lean body mass

These anatomical differences suggest that the same exercise may place different physiological demands on the female body such that it ultimately gains more health benefits.

“It is not surprising that women gained additional benefits, given that they have relatively lower levels of physical engagement,” Jennifer Sacheck, Ph.D., chair of the Department of Exercise and Nutrition Sciences at the George Washington University Milken Institute School of Public Health, tells Fortune via email. “The greatest benefits in health outcomes and mortality risk are when people go from nothing or very little to something.

“Thus, if women start at lower levels of physical activity than men, they get a lot of benefit from a small increase in physical activity.”

Who were the study participants?

Researchers reviewed two decades’ worth of data from the National Health Interview Survey, from 1997-2017, and linked participants’ records to those of the National Death Index through 2019. People with an array of preexisting conditions, from cancer to chronic bronchitis to coronary heart disease, were excluded. 

Of the remaining 412,413 people in the participant pool, 55% were women, 14% identified as Black, and 18% identified as Hispanic. Their average age was 44.

For more on the health benefits of regular workouts:

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