OPRAH WINFREY has lost a staggering 25 pounds in just six weeks – thanks to a new chef and the old treadmill.

Desperate to shed the extra weight she put on due to the stress of run­ning her OWN network for the past 18 months, the 58-year-old Emmy winner enlisted the network’s creative staff to help her find a nu­tritional regimen she could stick to.

What they found is a Hollywood chef who agreed to develop a cus­tom, three-meal-a-day portion-control menu designed completely around Oprah’s tastes.

The TV diva has also resumed tread­mill workouts with longtime trainer Bob Greene. And the results are nothing short of amazing!

 “Oprah has abso­lutely flipped for the new chef,” said a source. “The personalized diet Oprah’s been following uses a combination of fruits and vegetables, fish, chicken and lean meat. It’s low in fat and calories, but still leaves her feeling full.”

Oprah’s weight has been yo-yoing for years. But since she launched her struggling OWN network in January 2011, she’s been gaining consistently. “Deep down, Oprah knew she had the willpower to lose it again if she took the right approach,” said the source. “And she’s finally found a plan she really likes.”

According to the source, the plan focuses on choosing the right combi­nation of foods to generate energy. It includes meals and snacks that combine good protein, complex carbs and healthy fats. The diet can work for anyone who wants to lose weight.

“This program is a life­style change and it stresses eating the right kind of foods to sustain energy and good health,” added the source. “And Oprah just loves it.”