“American Idol” champ RUBEN STUDDARD is pigging out to cope with divorce and money woes – and pals fear he’ll eat himself to death!

The 33-year-old R&B singer has bulked up to nearly 400 pounds since filing for divorce from his wife of three years last November. And now experts warn that if he doesn’t lose weight, he’ll be lucky to see his 40th birthday.

“It’s diet or DIE for Ruben,” an insider told The ENQUIRER.

The 6-foot-4 “Velvet Teddy Bear” was already huge when he won “American Idol” in 2003, but he packed on even more pounds after that. He dropped nearly 65 of them while in a weight-loss program in 2006. But now he’s pushing the 400-pound barrier again.

“Ruben’s weight is extremely unhealthy and dangerous,” declared noted retired physician Dr. Gabe Mirkin, author of “The Healthy Heart Miracle.”

And leading New York weight-loss specialist Dr. Craig Title, who did not treat the morbidly obese singer, warned there is “a grave concern that Ruben will not make it to his 40th birthday at the rate he’s going.”

THE ENQUIRER previously reported that Ruben’s marriage to 34-year-old Surata “Zuri” McCants collapsed because of severe financial stress and his ballooning weight.

A judge recently upheld the couple’s prenup, giving Surata virtually nothing, but the tension of the bitter split still sparked Ruben’s gorging on comfort foods.

“Now his loved ones fear he will die tragically young,” said the insider about Ruben, who’s released a comeback album. “He agrees he needs to get help, and everyone is praying he’ll succeed.”