Serena Williams Reveals Her New Athletic Obsession — but Says ‘I Miss Tennis Like Crazy’ (Exclusive)

Serena Williams is on a health journey, and it involves an infamous jean skirt — and running a half-marathon!

The 23-time Grand Slam champion tells PEOPLE in an exclusive interview that she’s planning on running the race by the end of 2025, as she eyes getting even more fit two years after she stepped away from playing tennis.

“I’ve gotten obsessed, more obsessed with diet and exercise, I think, than when I was playing tennis,” Williams, 43, tells PEOPLE while talking about her new partnership with Lingo, a continuous glucose monitor from Abbott. “I knew that I was going to burn 20,000 calories a day, and now I’m like, ‘Oh my god, I don’t know how many calories I’m going to be able to burn!’ ”

Understandably, the busy mom of daughters Olympia, 7, and Adira, 15 months, whom she shares with her husband of seven years Alexis Ohanian, is focusing these days on managing her health — and fighting her natural inclination to view everything as a competition.

“Look at me,” Williams tells PEOPLE. “I’m trying to compete — not compete, rephrase — trying to do a half-marathon. That’s my new goal. So it’s just like I have to do something competitive. I miss tennis like crazy.”

She continues, “But as a woman, I had to make different choices that I probably wouldn’t have had to make if I were a guy, but that’s okay, I love that. I love that I chose my family and I want to be around them every single day of my life. And I try to do that, and I just figure I want to be the GOAT at something else. And for me, that’s being a mom right now.”

Along with her little girls, Williams is also making it a priority to invest in female entrepreneurs, through Serena Ventures, the venture capital fund she started in 2017.

In the new campaign with Lingo, Serena and Alexis, 41, share adorable and highly relatable moments from their lives, as they talk about the foods they enjoy and the impact they have on their bodies.

In the spots, done in what Serena jokes is like The Newlywed Game show, the two recall (and eat) what they had for their first date in Paris (roasted chicken and fries), their favorite things to enjoy with their daughters for weekend breakfasts (“Papa” pancakes) and Serena’s favorite savory and sweet late-night cheat foods (spicy instant ramen and gelato). All the while, their glucose is monitored by the wearable technology.

“I learned that I was a super-human and a superhero,” she laughs, about how her readings didn’t spike as much as Alexis’ did. “It didn’t affect me as much, but it still did affect me. At some point, you could see my level rising, which is why I always try to eat healthy. I’m all about a healthy lifestyle.”

To that end, the tennis icon is coming to terms with what exactly that means for her right now in this phase of her life.

“The more that I don’t play sports professionally, the more that I think, ‘Okay, this is what I’ve done for literally my entire life, and how do I optimize and keep it up?’ As a mom, my main goal is to be healthy for my kids and I have young kids and I need to be able to run for them and be able to do all that stuff,” she tells PEOPLE.

As for the aforementioned jean skirt — a figure-hugging, long denim number — she has not been shy about her desire to fit into the item in a hilarious ordeal she has chronicled on Instagram.

Sharing such behind-the-scenes moments is nothing new for Williams, who says she relishes her platform.

“Athletes and musicians, I feel like sometimes we think that we’re untouchable and that’s just not true,” she tells PEOPLE. “I literally don’t think of myself any different than anyone else. And I love to try to post relatable content. And I’m not doing it on purpose, it’s just who I am. I have the same struggles trying to fit in these darn skirts and I want to follow my health levels too. And I just think it’s so cool for people to see that, especially for me growing up in Compton.”

Williams adds, “It’s just like if there’s anyone else watching, know that. Knowing that I’m not any different from you. I’m literally the same. And probably, if anything, you’re probably smarter and better than I am. And that’s kind of what I always like to preach or show.”