Credit: Andrew H. Walker/Getty Images for BMI

Blake Shelton isn't one to spoil his fiancée Miranda Lambert -- especially when it comes to her birthday presents!

"I still haven't bought her crap yet," Shelton, 34, told Tuesday at the BMI Country Music Awards in Nashville.

Why so frugal? According to Shelton, his bride-to-be (who turned 27 Wednesday) is "rich. She can get anything she wants."

Not that Shelton, who is up for Male Vocalist of the Year at Wednesday's CMA Awards, won't treat her like a princess.

"I'll rub her back or something," he said.

Birthday plans aside, the couple told Us they've been busy getting in shape for their big day -- in their own ways, naturally.

"I got my trainer out on the road about 30 days ago," Lambert told Us. "It was time to get my butt kicked a little bit."

Shelton's approach to fitness, on the other hand, is less gym-focused.

"I'd rather starve myself than have to exercise. A month and a half before the wedding, I'll probably starve myself for awhile," he joked. "Lose a little weight, take the pictures and then go back."