Michelle Obama, who turns 50 later this week, hasn't ruled out plastic surgery or Botox in the future.

"Women should have the freedom to do whatever they need to do to feel good about themselves," the first lady told People magazine in an interview hitting newsstands Friday, her birthday. "Right now, I don't imagine that I would go that route, but I've also learned to never say never."

Her message to women is to be healthy. Obama says she has never missed a health checkup, including mammograms and Pap smears. She's also had a colonoscopy.

"I don't obsess about what I eat, but I do make sure that I'm eating vegetables and fruit," she added. "And as everyone knows, I do exercise."

Her "Let's Move" campaign to reduce childhood obesity rates through the combination of exercise and healthier eating enters its fifth year next month.

PHOTOS: Michelle Obama Through the Years

Her workouts have also evolved from weight-bearing and cardio to include exercise like yoga that she says will help keep her flexible.

Asked whether she has peaked at 50, Obama joked that being first lady is "pretty high up."

She said she has always felt that her life is "ever-evolving" and she doesn't have the right to "just sit on my talents or blessings."

The president is reportedly planning a White House party Saturday to mark his wife's birthday. Guests have apparently been told to come ready to dance, and eat before they come.

At 50, the first lady says she is "more self-assured now. Each decade just brings a greater sense of calm and certainty and maturity and confidence."

She also wants to try to use the big occasion for good, People correspondent Sandra Sobieraj Westfall said.

"She wanted to really use this milestone and the spotlight on her during it to help other women promote the kinds of things she's doing with her own health care," Sobieraj said.

The first lady's birthday wish? To be with the people that she loves.

Michelle Obama's Early Birthday Gift

She has already received an early gift: spending extra time with her close friends, including Oprah Winfrey, in Hawaii after her family's holiday vacation there, an early birthday present from the president.

The real celebration kicks into gear Saturday, a chance for the first lady to dance, a milestone birthday on Pennsylvania Avenue.

The Associated Press contributed to this report.

(Photo Credit: Jewel Samad/AFP/Getty Images)