The model was in Johannesburg this week to take part in Mercedes-Benz Fashion Week, modelling lingerie for the Dax Martin Chocolatier Collection.
In an interview, she said that she was now based in Nairobi.
"I made the decision to go back home last year. I love my country. I also wanted to be with my family and to start giving back to my community," she said.
The beauty has been married for 12 years to Gustav Ericson, who, she said, was her "first and only" boyfriend. The couple have a two-year-old son.
She said that, in between her modelling assignments, she had started a foundation that looked after pregnant women in hospitals.
"I have always wanted to be a midwife, but I don't have time to study, so I am creating a caring and sensitive environment for pregnant women."
Nasenyana said the idea to revamp maternity wards came after she gave birth to her son. She said hospitals in Kenya were not up to the same standards as those in developed countries.
Born in a nomadic tribe in Turkana in northwestern Kenya, she was raised by her single mother, Maria, who runs women's groups that teach villagers about HIV/Aids and abuse.
Although she enjoyed the opportunities modelling afforded her, she advised women in her village that they had to aim higher in life.
"I tell them, 'You are more than being desperate to be a model. You can do better with your life.'"
Now that she is back at home, she has started negotiating to endorse products that will help change the perception that only light-skinned girls are beautiful.
"It's not about the money; it's about encouraging girls and uplifting them, because I did not feel beautiful while growing up."
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