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Health

Almost everyone she knew growing up were laborers. Now she researches inactivity.

Epidemiologist I-Min Lee has published hundreds of papers on exercise and heart health in her time with the Harvard Alumni Health Study and the Women’s Health Study

Sy Boles

Harvard Staff Writer

July 27, 2026

5 min read

Part of the
Profiles of Progress
series

I-Min Lee got used to being the odd one out at conferences when she first began researching the role of exercise in health and disease-prevention.

“A lot of people in this area were athletes in college, or they played a sport, or were ballet dancers,” said Lee, a physical activity epidemiologist. She recalled standing around feeling awkward while colleagues discussed marathon times.

Working out didn’t come naturally to Lee. While growing up in Malaysia in the 1960s and ’70s, just about everyone she knew labored under the hot tropical sun or as domestics. They got plenty of exercise. Every parent’s fondest wish was that their children would get desk jobs in air-conditioned comfort.

“If you had a seated job, you’d made it. You didn’t have to work in the fields,” she said.

Now a Harvard Medical School professor of medicine at Brigham and Women’s Hospital and a professor of epidemiology in the Harvard T.H. Chan School of Public Health, Lee got her desk job. But she’s also keenly aware of the potential drawbacks for health that can come from such a lifestyle.

“I don’t even have to get up to go to the fax machine anymore,” she said. “I can just sit and do everything on my phone or computer, and that’s really bad, I think.”

The principal investigator of the long-running Harvard Alumni Health Study and the Women’s Health Study, Lee has published some 650 research papers on associations between physical inactivity and noncommunicable diseases such as heart disease, diabetes, and cancers; dose-response relationships between physical activity and health; and population-level effects of physical inactivity. Her research helped inform the 2008 and 2018 federal physical activity guidelines.

Lee is quick to note that she fell into this line of work by accident — though certainly not without effort. She finished medical school in Singapore in 1984 and developed an interest in biostatistics, which led her to a master’s program at the Chan School.

She liked the work and was thinking about a doctorate, but some of her professors tried to warn her off it. She wasn’t a U.S. citizen, so she would be disadvantaged or ineligible for certain scholarships and grants. She had better be very certain it was really what she wanted.

Around that time, Lee met Ralph Paffenberger, the superstar epidemiologist who founded the Harvard Alumni Health Study in the 1960s and wrote some of the earliest papers connecting exercise to heart health and longevity.

Lee hadn’t studied exercise before, but she liked “Paff,” as he was commonly known. She worked with him on her Sc.D., which she finished in 1991, and would go on to work with him on the HAHS, expanding the research to include women and demonstrating more conditions helped by physical activity.

She’s also taken up running — both because she knows it’s good for her and because she was tired of feeling embarrassed at industry events (peer pressure advocates, take note).

But she remains an epidemiologist for those of us who would feel out of place comparing PR running times.

“If you’re an NFL athlete or a champion gymnast and you’re in this field, I think in some sense the public, most of whom are not active, can’t relate to you,” she said. “If I can do it, I tell people, you can do it. I’m just looking for a reasonable amount of activity for a regular person.”

It’s an important time for the message.

Nationally, only 24 percent of U.S. adults met federal guidelines for both aerobic and muscle-strengthening activity in the most recently available data. About 46 percent met neither aerobic nor strength guidelines.

And our health is suffering for it.

Three out of 4 American adults have at least one chronic condition such as heart disease, cancer, or diabetes, many of which can be caused or worsened by behaviors including physical inactivity.

It’s also an important time for science. Although wearable fitness trackers have been widespread for decades, the data they provide is just beginning to mature.

Researchers like Lee, who once had to rely on self-reported activity data, can now answer much narrower questions about what kind of movement, and how much, really contributes to health.

Using wearable data, Lee was among the first researchers to question the common goal of 10,000 steps per day.

In a 2019 study in JAMA Internal Medicine that looked at all-cause mortality in some 16,000 older women, Lee and colleagues found that women who averaged 4,400 daily steps had a 41 percent reduction in mortality over sedentary women, and mortality rates progressively improved with more steps until they leveled off at about 7,500 steps.

Later research has shown that sedentary adults start to rack up benefits from movement with just an extra trip around the block — 500 to 1,000 steps.

The findings are heartening, Lee said.

“For people at the lower end [of physical activity], people who do nothing, they see a recommendation to get 10,000 steps and they think, ‘I can’t do that, so I might as well not get started,’” she said. “But with the research, now we can tell them that any little bit is better than doing nothing.”

Lee believes that the influx of fine-grained data will help inform the next iteration of our federal guidelines to include step metrics. The goal, she said, isn’t to shoehorn every person into a single set of activities: It’s to help everyone find the kind of movement that works for them at their current stage of life.

“It’s more like giving people a better way of living,” she said.