Trying to eat healthier? Great. Just avoid this common mistake: eliminating entire food groups from your diet. It's a common weight loss tactic. Most often, dieters will snub carbohydrates — you know, like all of those fad diets you've been trying to follow for the last two (or 10) years.

Everyone from Kim Kardashian and Megan Fox to Matthew McConaughey have been quoted embracing the no-carb diet. Yet, we're reading more often that eliminating entire food groups is a recipe for disaster.

I decided to turn to the professionals for help in understanding what it is that makes them cringe about no-carb diets.

But first, let's go back to basics: What exactly is a carb?

Carbohydrates are a type of macronutrient found in many foods and they come in a variety of forms, mostly sugars, fibers, and starches.

The issue with eliminating carbs from your diet lies, first and foremost, in the fact that your brain needs carbs to function.

"Scientific studies show that the brain needs 130 grams of carbohydrates a day to function properly," said Theresa Shank, RD, LDN of Einstein Healthcare Network.

Kelly Strogen, MS, RD, LDN, of Club La Maison on Philadelphia's Main Line, explains the process further:

"Your brain and muscles run primarily on glucose, and carbs break down into glucose, so the only way to get stronger both mentally and physically is to consume carbohydrates."

Strogen says she's not a fan of any elimination diets — carbs or otherwise — since eating from a variety of food groups ensures that the body gets all of the proper nutrients it needs to survive. Subsequently, when you eliminate food groups, you put your body at risk for a number of nutritional deficiencies. In the case of cutting carbs, you're also cutting out essential vitamins.

"A lack of whole grains eliminates a lot of fiber and B vitamins from your diet, which help you feel fuller longer," said Strogen. "Eating bulgur or millet isn't going to cause you to gain weight."

Ketosis, an unhealthy metabolic state, is another issue that dietitians worry about. In the absence of carbs, the body begins to burn its own fat for fuel — which my sound like music to a dieter's ears, but in reality, substances known as ketones build up in excess and cause you to experience headaches, nausea and bad breath.

Yet, most importantly, professionals tend to steer their clients away from elimination diets simply because they are not sustainable in the long run.

"I've found that people who eliminate carbs are the one's that struggle the most with their weight," said Strogen. "These dieters almost always fall off the wagon and then binge on things like pizza and brownies, or they over consume other food groups, which is just as unhealthy."

When it comes to diets that restrict carbohydrates, the amount of carbs in the diet is less important than the type of carb. The CDC identifies "good" carbs as those that are naturally occurring in plant-based foods (i.e. fruits, whole grains) and provide dietary fiber without added sugars.

"Refined flour, for example, is essentially similar to eating skittles in the way your body breaks down the sugar," said Strogen, "So I tell my clients that if it's not whole grain, don't even touch it."

Shank says anyone following a no-carb diet would need to be medically supervised and should last no longer than 6 months. However, a low-carb diet, if executed safely, is something she can get behind.

"I can't support a no-carb diet but given that the average American is mostly sedentary, their bodies don't need as many carbs," said Shank.

According to the 2010 Dietary Guidelines for Americans, carbohydrates should account for 45 to 65 percent of your diet, or 225 to 325 grams within a 2,000 calorie-per-day diet. For clients who are looking to lose weight, Shank recommends they aim for 40 percent of their calories from carbs.

"As long as you're still incorporating healthy amounts of dairy, fruits and vegetables, you're still getting good sources of fiber in your diet," said Shank.

"But at the end of the day, losing weight is all about calories in and calories out."