Why does Oprah constantly do this to us? She has Gwyneth Paltrow on her show today, and Gwyneth talks about her fabulous fit self, and then reveals the secret to her (and Madonna’s) incredibly cut post-baby bodies.

It’s fitness guru Tracy Anderson, a 5-foot tall, super-sculpted personal trainer from L.A. who has been working with the celebs for two years. The buff guru has kept a relatively low profile until - coincidentally? - she decided to release three DVDs this month that showcase her special method, honed after years of intense study, her Web site says.

She created a machine called the Hybrid Body Reformer that moves in all kinds of unusual ways that are far too complex to be explained in this small space. But she’s apparently doing something right if her flat-bellied clientele are any indication. She says she plans to expand to New York, and is currently on tour with Madonna. The new DVDs, all $30, are a mat workout, a dance cardio workout and a post-pregnancy workout.