Blake Shelton’s been packing on so many pounds his wife, Gwen Stefani, wants to ship him off to a “fat farm” to cure his deep-seated issues with overeating and his love of fattening fare like country fried steak, mashed potatoes and Velveeta dip.

“His weight yo-yos up and down, he’ll lose weight and then go right back to his bad habits and pile it all on again,” a source exclusively tells Life & Style. “Everyone agrees something needs to change for the sake of his health.”

In January, the country star, 48, who’s 6-foot-5, showed off a slimmed-down frame on CMT Giants. But leaving The Voice last year has left him with lots of downtime, which has been disastrous for his diet, the insider says.

In the past eight months he’s packed on more than 30 pounds, the source reveals. “He’s tipping the scales at 250 pounds, which is way past healthy. He admits he needs to lose at least 20 pounds, but he can’t seem to stick to a healthy diet no matter how hard he tries. He’s going hog wild on barbecue pork sandwiches with all the fixings and all his other favorite foods. Gwen’s obsessed with her diet and she’s worried he’s on his way to being obese. Clearly, his body-fat ratio is less than ideal. She’s convinced Blake will feel better if he loses 20 pounds.”

Gwen, 55, returned as a coach on The Voice this season so she doesn’t have time to monitor the “Honey Bee” singer. “She can’t watch him every second, which makes a weight loss facility even more appealing,” the spy says. “He can get professional help, exercise and understand why he’s reaching for the potato chips and beer, and get his weight back down to a healthier place.”