The controversial eating plan involves a whole lotta steak.

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Fueling better performance at the gym has inspired some interesting eating habits-some backed by science (like beet juice shots) and some, well, not so much. Falling in the latter category is the Vertical Diet-a eating plan favored among CrossFitters that's causing major controversy. (Haven't jumped on the Crossfit train? Read this before you add CrossFit to your workout routine.)

The Vertical Diet says it's all about building muscle and fueling athletic performance, according to the diet's body-builder founder, Stan Efferding. Sounds great for your gym game so far, right? But the actual eating plan raises some major objections from registered dietitians.

First, What Is the Vertical Diet?

The diet gets its name from its version of the food pyramid-an upside down "T". On the bottom, representing small portions of the daily diet, the Vertical Diet emphasizes "a solid foundation of highly bioavailable micronutrients." Think vitamins, minerals, and antioxidants found in fruits and veggies. But the majority of your foods-the vertical part of the upside down "T"- are supposed to be predominantly red meat and white rice. No lean poultry or omega-rich fish. No fiber-rich whole grains. No pulses or legumes.

Is the Vertical Diet Even Healthy?

Proponents of the diet claim that the protein and carb-packed eating plan will optimize gut health, correct nutrient deficiencies, and boost "energy, stamina, endurance, and recovery," according to the diet's website.

Aside from the fact that heavy red meat consumption has been linked to an increased risk of breast cancer, heart disease, and diabetes, nutrition experts are straight-up skeptical about the Vertical Diet's health claims.

First up, gut health. "Fiber is one of the most important food components required to improve digestion-since the Vertical Diet is very low in fiber, this process would be hindered and can eventually cause constipation, bloating, and gas," says Alissa Rumsey, R.D., C.S.C.S. "The Vertical Diet also eliminates foods like oats and onions, which are sources of prebiotics, the foods that gut bacteria need to flourish," she says. Fiber is also important to your body's ability to absorb nutrients from food-"it slows down the time it takes for food to move through our digestive system, which means more nutrients are absorbed," along the way, says Rumsey.

Plus, despite the supposed focus on getting more micronutrients, the Vertical Diet seriously restricts or limits a lot of nutrient-dense foods, such as beans and whole grains, says Keri Gans, R.D. "I don't know why anyone would want to limit their number of nutrient-dense foods-we recommend to seek out nutrient-dense foods," she says. (Related: Magnesium Is the Micronutrient You Should Pay More Attention To)

But Does the Vertical Diet Help with Fitness Gains?

Aside from its wide nutritional gaps, the Vertical Diet still claims to help you build muscle and boost endurance and recovery. Is the bogus, too? Potentially-but it's probably not the healthiest way to reach the same results. "It's old school to think that only red meat provides protein," says Gans. "While you do need to replenish your protein stores to build muscle mass and repair muscle, protein comes in many sources including nuts, seeds and plant sources like soy." Most people are already getting plenty of protein in their diet without having to go crazy on the steak, adds Rumsey. (See: Easy 4-Ingredient Recipes for Post-Workout Muscle Recovery)

The Verdict On the Vertical Diet

The experts we spoke to object to the overall premise of the Vertical Diet. "We know that restrictive diets like this that cut out certain foods or food groups never work in the long run-they are not sustainable," says Rumsey. "When you start to restrict types and amounts of food your body switches into survival mode, which can mean uncontrollable cravings, overeating, and binges." (Related: What It's Really Like to Be On an Elimination Diet.)

"This is just another restrictive diet plan," says Gans. Instead of "going vertical," try a healthier "horizontal" way of eating-meaning, filling your plate with foods from various food groups. "Your body will get the macronutrients (carbohydrates, fat, protein) and micronutrients (vitamins and minerals) it needs when you eat a varied diet," says Rumsey. "Eating different fruits, vegetables, whole grains, pulses, nuts, and seeds will ensure that your body is getting enough of what it needs."