04/17/2013 at 05:00 PM EDT
When she learned her husband, Garth Brooks, would be singing at the April 7 Academy of Country Music Awards alongside his hero George Strait, Trisha Yearwood began searching for "arm candy" attire to wear to the Las Vegas event.
That's when she spied that dress – a form-fitting Stella McCartney column that she'd first admired on Kate Winslet in 2011. "I'd been working hard and losing inches, but I wondered, 'Can I fit into that?'" Yearwood recalls. The answer was a jaw-dropping yes. "It was tight!" says Yearwood, but "I felt confident. It was a wow dress."
Not to mention a wow moment for the Grammy-winning star, 48, who lost an astounding 30 lbs. from her 5'9" frame in the last four months.
"My butt and my waist are smaller, and I like seeing that in the mirror!" says Yearwood. "But I also feel great." So good, in fact, that on her flight back to the home near Tulsa she shares with Brooks, 51, "we got on the plane, the sweats were on, and I had an In-N-Out burger with fries and two dark chocolate Reese's cups!" she says.
In years past, she adds, "if I did that, I would have said, 'You just screwed up, so might as well go out and have 20 cheeseburgers,' and I would. [This time] I got on my treadmill the next day, I ate well and I didn't do any damage. That's what real people do."