4 Easy Diet Rules Carrie Underwood Swears By

Diets are rough. Mostly because the second you start one, you typically have to stop eating everything you like to eat. Thank goodness that's not the case for every plan. Erin Oprea, celebrity trainer and former Marine, only requires you to abide by four steps to transform your body.

Need proof those steps work? Two words: Carrie Underwood. A longtime client of Oprea, the musician credits the trainer with her fit physique. And the plan that keeps her healthy and happy is available in Oprea's book, The 4x4 Diet, which focuses on changing the way you look and feel with four key foods and 4-minute workouts.

It might be called a diet, but it's really not. As Underwood writes in the book's foreword, it's more of "a lifestyle" that focuses on eating as cleanly as possible. And the best part? There's no counting calories.

"Your life doesn't have to be around measuring everything you eat and obsessing over it. Just learn to eat clean foods and eat until you're content. How many people are going to overeat zucchini noodles?" Oprea says. "With healthier foods, it's OK if you eat more than 3 ounces of grilled chicken breast. Unlike eating fried chicken, you won't keep eating and gain weight."

Follow these four easy tips to start seeing positive changes to your body and mood.