In less than a month, Texas beauty Miranda Lambert will become Mrs. Blake Shelton. But right now, Lambert is on the May cover of Health, in which she opens up about how she has been getting slim -- not only for her wedding day, but for her overall well-being.

Within the last year or so, the 'Heart Like Mine' singer has gone from a size 10 to a size 6, and she did it the old-fashioned way.  "I wanted to get in better shape and wanted to keep it going for the wedding," Lambert says. A trainer helps keep Lambert "in check" on the road, and she reveals, "We do a lot of circuit training, lunges and crunches. And every morning, we walk for 30 minutes."

What the country star eats has played a huge role on her road to getting healthy as well. Gone are past favorites like mayonnaise and chips. Instead, "I eat a lot of protein and eat pretty clean," Lambert says. "Junk food drags you down. It's a conscious decision every day to eat something healthy vs. not healthy."

Lambert, who has to keep her energy high while performing, has a method for feeling good onstage: "I try not to have anything less than two hours before I go on stage, because I don’t want to be up there all bloated. I basically have a grilled chicken salad after the show, and that fills me up."

Lambert recently revealed that no matter what size she is, Shelton still has "loved me at all weights, so if I gain 30 pounds before [the wedding] -- I don’t want to! -- but he’ll still marry me." Shelton has gushed, "She looks amazing! She set a goal for herself, worked hard and I am so proud of her."

The issue of Health with Lambert as its cover girl hits newsstands on Friday, May 22.