The My Life in Ruins star got fit and dealt with a fertility struggle with a faithful four-legged friend

After receiving doctor’s orders to shed some pounds, My Life in Ruins star Nia Vardalos decided the celebrity trainer route that many stars take wasn’t for her. Instead, she enrolled in the “Manny 6-Lb. Challenge.”

Who’s Manny? Manny is the 6-year-old purebred Labrador Retriever the actress adopted, who has been an integral part of her workout routine.

“The two of us lost weight together,” she told PEOPLE Pets in an exclusive interview. “The vet had just told us that he was a little bit overweight, so we called it the ‘Manny 6-Lb. Challenge.’ ” In addition to sticking to a diet program she designed herself and “breaking up with cheese,” Vardalos stayed active with daily walks and play time with Manny, who loved running after a particular tennis ball. The routine became a game for the actress’s 4-year-old daughter, whom she adopted last year with actor husband Ian Gomez.

“[Manny] loves to chase a yellow tennis ball. We taught him, ‘Drop it, drop it,’ and it’s really funny to hear our daughter say, ‘Manny, drop it, drop it,’ ” she says.

Vardalos, who got her big break in 2002’s My Big Fat Greek Wedding, adopted Manny four years ago, after a 10-year struggle with infertility. Her doctor suggested adopting a canine companion, and she admits, “It was the best advice I’ve ever been given.”

The pooch brought her comfort after a very difficult time. “He was actually part of my healing,” she says of the dog. “We got him as part of the end of the fertility road.”

The actress has to thank for finding Manny. After entering search terms and her location on the Internet, within days the actress welcomed the new pup into her home, which he now dutifully protects. “He’s sweet,” she gushes. “He’s kind and he’s a ferocious beast when it comes to anybody at the front door. He has a bark like a lion.”

When he’s not staying active, Manny passes the time with rawhide chews and plenty of sleep. “He sleeps at the foot of our bed until he snores,” she says.

Read more about how Nia Vardalos got back into shape in the new issue of PEOPLE, on stands now.