"To get my abs, I obviously combine a lot of cardiovascular training, and you don't have to get on a treadmill," the Bravo reality star tells Us. "I've always said that crunches are a waste of time. I've got pretty good abdominals, but I don't do crunches."
So what does she recommend?
"A simple push-up is a much better core exercise than a crunch," she says.
For two variations on the simple push-up -- including a "T-plank" push-up and the side plank -- watch the clip above.
Warner also shares her tips to "clean up your diet," an integral part to defined abs.
1. Eat more veggies
"You have to really increase your vegetables and things that actually speed your metabolism such as eggs, which contain lecithin," Warner says. "Eat two eggs a day."
2. Add lemon juice to water
"Here's a simple trick," she says. "Add organic lemon juice to your water every day, and drink three liters of water. Adding 500 milligrams of ascorbic acid to your diet can speed up your metabolism by 33 percent."
3. Eliminate sugar
"Fat does not make you fat -- sugar does," she tells Us. "It's in everything, it's hidden. The body doesn't even register five grams and under, so as long as you keep it there, you don't have the insulin spikes and drops, which is key for weight loss."