Epidemiologist Carmen Harris has seen how public health changes and improves lives.

Everybody in her family — with the exception of her dad — smoked. Her grandfather died of Alzheimer’s disease and lung cancer.

No one in her family smokes anymore.

When her aunts and uncles needed to lose weight, Harris saw them shed pounds. She grew up playing soccer and walking with her mother and sister. Her dad ran in 5K and 10K races, and he remains active today. Now, when Harris visits her aunts and uncles, she’s expected to hit the senior center with them.

“I’ve seen the beautiful side of when you change the expectations or you change the narrative,” Harris said. “You literally change a generation of health in your family.”

Harris is now the chief of social impact and strategic partnerships at GirlTrek, a nonprofit that encourages African American women to take control of their health, families and communities by walking. There are now 647 GirlTrek teams across the United States.

GirlTrek honors the sacrifices of women who came before them, including Fannie Lou Hamer, a civil rights crusader who died at 59 from complications associated with heart disease and untreated breast cancer. Both are chronic diseases, which GirlTrek is dedicated to preventing.

On Oct. 6, GirlTrek will celebrate what would have been Hamer’s 100th birthday. Women who are foot soldiers of #FanniesArmy will lead 100 walks for 100 minutes nationwide. GirlTrek’s national staff — including cofounders T. Morgan Dixon and Vanessa Garrison — will walk with local trekkers in Ruleville, Miss., Hamer’s hometown.

“We lost this woman way too soon due to health conditions, and that’s part of where GirlTrek comes in,” Harris said. “It’s this beautiful intersection between justice — how to honor the work that women are doing — and health.”

Eighty-two percent of African American women ages 20 and older are obese, according to CDC data from 2011 to 2014. The leading causes of death for black women are heart disease, cancer, chronic lower respiratory disease and stroke.

Part of GirlTrek’s mission is to change these statistics. Black families — including Harris’s — have dealt with generations of systemic oppression that have contributed to poor health among African American communities. They were not set up to succeed.

“We get to choose our narrative,” Harris said. “That is our family taking back our health.”

“That is the beautiful thing about what lives inside of people when you give them the opportunity, information, knowledge and access to change,” she added. “My family has gotten to experience that.”

Before GirlTrek, Harris spent 10 years at the Centers for Disease Control and Prevention in its division of nutrition, physical activity and obesity.

“I really took away how much physical activity impacts our health, particularly African American women and girls and children,” she said.

What attracted her to GirlTrek was how actively the organization pursued solutions. They were actually getting people walking.

For optimal health benefits, the CDC recommends that Americans do 150 minutes a week of moderate-intensity exercise. But when Harris first met with the GirlTrek cofounders, the organization was taking it a step further. They wanted participants to establish a daily habit of walking by moving 150 minutes a week for three months or more. That threshold impressed Harris.

“I was like, ‘Whoa, this is for real,’” she recalled. “‘Y’all are doing it right.’”

“[GirlTrek is] helping the next generation of black girls become healthy,” Harris said.

When Harris left the CDC in Atlanta for Washington, she sold her car. For her, walking is a lifestyle. Sometimes, she is a solo trekker. Other times, she is walking alongside women who find peace and purpose on their weekly walks. On a recent GirlTrek trip to Rocky Mountain National Park over Labor Day weekend, she was reminded of walking’s healing powers.

“A woman came up to one of our cofounders, Vanessa, and said, ‘My son was just killed on July 5,’ and then she quietly walked away,” Harris recalled. “Vanessa shared this with our group. Being together was creating a healing space for women.”

Throughout the rest of the weekend, other women shared their stories. One person told Harris that 11 years ago in September, she had lost her husband. GirlTrek, Harris realized, is a “place where black women are together, and they feel safe.”

“I’ve just been ruminating on that story,” Harris said. “All of this loss, but this is a healing opportunity together.”

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