Cutting carbs can be healthy. But sustaining a low-carb diet may not be for you.

While diets can certainly range from healthy and helpful to worrisome and even dangerous, they all have at least one thing in common: a focus on reductions and eliminations.

Examples include the Mediterranean diet recommending cutting down on processed foods and red meat, the Whole30 diet eliminating added sugars and alcohol for a month or the carnivore diet asking its participants to exclude fruits and vegetables. Even the healthiest of diets like the DASH diet recommends limiting sodium intake. 

Though some dietary exclusions make more sense than others, a few foods seem to be recommended against especially often. One of the most targeted nutrients of many of the most popular diets is carbohydrates.

What are carbs? 

Carbohydrates, commonly called carbs, are the sugars in specific foods. The are important because they are the body's main source of energy.

There are two main types of carbs: simple and complex. Simple carbs are natural, digestible sugars such as ones found in foods like milk (lactose), table sugar (sucrose) and fruit (fructose). Complex carbs are starches and the fibrous parts of food that the body doesn't digest. Complex carbs are commonly found in starchy vegetables like potatoes and corn or processed grains like rice, bread, cereals and pasta. 

Both simple and complex carbs are broken down by the body into glucose, which gets transported to cells, muscle and organs to provide energy. 

What is a low-carb diet? 

A low-carb diet aims to limit the amount of carbohydrates you eat. Most healthy adults eat between 225 and 325 grams of carbohydrates a day, but low-carb diets recommend significantly reducing this amount to no more than 130 grams daily. "Some are restricted to as low as 20 to 60 grams of carbohydrates per day," says Leslie Bonci, a sports dietitian for the Kansas City Chiefs and founder of Active Eating Advice.

Such restrictions occur by cutting down on candy and sugary drinks, starchy vegetables and processed grains. A food's "Total Carbohydrates" are listed on its Nutrition Facts label.

Dieters are encouraged to replace high-carb foods with low-carb alternatives such as chicken, seafood and lean beef, plus fruits like apricots, oranges, avocados, raspberries and lemons. Vegetables like broccoli, tomatoes, mushrooms, onions, kale and asparagus are also included in most low-carb diets—as are eggs, cheese, Greek yogurt and nuts like walnuts, peanuts, macadamia nuts and pistachios.

"The focus of a low-carb diet is on eating more protein and fat for nutrients and energy instead of high-carb foods," says Lisa Young, a registered dietitian nutritionist, author of "Finally Full, Finally Slim" and an adjunct professor of nutrition at New York University.

Some of the most common low-carb diets include the ketogenic (keto) diet, the Paleo diet, the South Beach diet, the Dukan diet and the Atkins diet. 

Are low-carb diets good or bad for you? 

Like most diets, there are advantages and disadvantages of low-carb dieting. Some of the benefits include decreased risk of certain mental and physical health conditions, improved blood pressure and reduced calorie intake—which can help with weight loss. Young says that low-carb diets can also be helpful for blood sugar regulation as they recommend foods low on the glycemic index and they usually provide lowered triglycerides—a type of fat in the blood that can increase your risk for heart disease.

The emphasis on higher amounts of fat and protein "may also result in feeling fuller for longer and less hungry between meals," says Bonci. 

But low-carb diets can also be disadvantageous by being "hard to sustain and may unnecessarily restrict nutrient-dense foods like fruits, beans and whole grains," says Young. Such foods, she says, "are essential for everyday gut health, heart health and overall well-being." 

Longterm adherence to stricter low-carb diets, Young adds, can also "lead to increased cholesterol levels from excessive saturated fat and nutritional deficiencies." Low-carb diets have also been clinically associated with constipation (due to the lack of fiber), moodiness and increased risk of kidney stones. 

Bonci points out that low-carb diets can also be pricey, "as typically carbohydrate-containing foods are less expensive than protein food," she says. Some brand name low-carb diets—especially ones with designated meal plans—can get costly.

In the end, "being mindful of excessive carbs is smart, but balance is key as overly restrictive diets can backfire," cautions Young. "A sustainable, healthy diet includes a variety of nutrient-rich foods in balanced portions."