Amy Tan: Best-selling author and fitness buff?

In an unlikely story of transformation, the writer of “The Joy Luck Club” recently revealed her newly toned body in a Facebook post. At 64 years old, Tan is proudly flexing her biceps for all to see.

“In November 2014, I made a plan to change my hair color to blue and build core body strength to prove to myself that age doesn’t mean that everything ‘goes downhill from here,’ ” she wrote in a message on the social network.

The award-winning author added that she’s suffered from Lyme disease, frequent injuries and osteoporosis, which left her unable to do simple tasks like pick up luggage. Nearly two years ago, Tan adopted a rigorous workout routine to combat her weakness with the help of personal trainers Andy Johnson and Tom Mayock.

It paid off big time.

“Working out after age 60 makes a big difference in strength, balance, and endurance,” she said. “Having blue hair is fun.”