The key to losing weight and building lean muscle is to have your body's metabolism working at its best. Therefore, I'm a huge advocate of one-ingredient foods because they're easily recognizable and digestible in your body. This is critical when it comes to absorbing all the nutritional value of your meals, but also for completing that exchange of unwanted pounds for lean muscle tissue.

What is a one-ingredient food you ask? Exactly what it sounds like: It’s a food with a single ingredient. For example, when you hold an apple in your hand, or a sweet potato, or a blueberry, it only has one name to describe it. Nothing added. It just is what it is. They're right in front of you…everywhere!

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Simply look at the nutrition facts of the foods you have at home to get more comfortable with this concept. By law, every ingredient must be listed so read up on what you’ve been ingesting. If there's a looong ingredient list or if there are things that you don’t even recognize or can't pronounce, then I would urge you to change out that item in your meal plan for something with as few ingredients as possible.

Ultimately, I want a very wholesome look to your plate at every meal—not just one a day or two per week. Consistency in this way of eating is necessary to support the strong, beautiful build you want. Swap in as many one-ingredient foods as you can in the correct portions for you. Bright orange sweet potatoes. Deep green cruciferous vegetables. A flaky, white fish flavored with only lemon and herbs. This is what I need to see in order for your muscle tissue and energy needs to be supported as well as for your metabolic furnace to stay in play.

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Jen Widerstrom, a trainer on The Biggest Loser, has a holistic approach to health and wellness that incorporates nutrition, fitness, and mental well-being. Check out her Health cover story, Jen Widerstrom's Shape-Up Secrets. She'll be taking over the @HealthMagazine Instagram account on Wednesday, January 14. Follow along at #JenWiderstromforHealth.

Photo: James White