Tori Spelling is toned, tanned and turning 40! To celebrate her milestone birthday May 16, the native Californian flew South of the Border with her favorite six people. "While I could be spending my day in denial, instead I'm on a beach in Mexico celebrating the occasion with my whole fam and my bestie," Spelling wrote on her official blog. "Because hey, I'm proud of all I've accomplished in these 40 years. In fact, I can't wait for the next four decades. Bring 'em on!"

The bestselling author was spotted wearing a Mara Hoffman bikini in Cabo San Lucas on Saturday, May 18. One month earlier, the Beverly Hills, 90210 actress put on a bikini for the first time since her son Finn's birth in August 2012 and showed off her incredible post-baby body in an exclusive Us Weekly photo shoot. (Spelling and husband Dean McDermott are also parents to Liam, 6, Stella, 4, and Hattie, 19 months.)

"I've had so many kids, I'm not sure what my old size is! But I feel like I took the weight off safely, and I'm totally happy here," Spelling said of her 45-pound weight loss. The Mistle-Tones actress makes fitness fun for her family, taking her kids to Bas Rutten's Elite MMA Gym in Westlake Village, Calif., for an hour once a week. "They're extremely family-oriented," Spelling told Us of the facility. "The kids take classes, the babies play on the mat and Dean and I do an adult training session."

Spelling regularly takes her kids to the park, where they'll embark on two- to three-mile walks. "We have a lake near us, so we don't even go to a trail," the Oxygen reality star said. "I put the babies in a double-wide stroller and bring an extra for when Liam or Stella gets tired."

Eight months after giving birth, Spelling is proud of her figure -- but not for the reasons one might think. "I am in awe of it," she admitted. "I think, 'Wow, I made four human beings.' I feel like I can do anything at this point. I praise my body every day. I am so grateful for it."