Carrie Underwood in Training for Wedding

Carrie Underwood may be busy planning a wedding and kick-starting a new tour, but she's not going to let herself go in the process.

The slim singer, 26, recently became engaged to hockey boyfriend Mike Fisher -- and admits that she'll work extra hard to keep her trim figure for their wedding.

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"Genetics are not exactly on my side," Underwood, 26, says in an interview with Ottawa radio show Grecosize, as reported by Us Weekly. She adds, "I carry all my stress weight, all my potato chip weight, around my midsection. You've got to fight genetics sometimes."

To fight any extra weight, Underwood reveals that she skips fancy catering on tour and buys all of her own food. "I do not eat catering. I have a refrigerator on the bus and when we're in a decent town that has a decent grocery store, I just go and stock up. My off days on the road are spent doing laundry and buying groceries."

Her new personal trainer, Tony Greco, is "kicking my butt," she admits. "I need it... especially with a tour coming up and a wedding to look good for."

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Carrie says that the happy couple has "no date" set for their wedding, but their aiming for a summer ceremony. "We're hoping the summer will be some nice time for us to spend consecutive days together."