Instead of restricting all carbs, she recommends prioritizing a specific type of carb.

By Renee Cherry
July 30, 2019

Many popular diets call for restricting a food group, and carbs often take the hit. For starters, the keto diet is one of the buzziest diets right now and one of the most extreme when it comes to carb restriction. In order to stay in ketosis, dieters aim to keep their calories from carbs at no more than 10 percent of their total calorie intake. Plus, plenty of keto's popular predecessors, including the paleo, Atkins, and South Beach diets, are also low-carb lifestyles. (Related: How Many Carbs Should You Eat In a Day?)

Not everyone is buying into the low-carb diet trend, though. Amid the popularity of the diets, nutritionists have spoken up about existing evidence that carbs don't always lead to weight gain, and that giving them up can come with nasty side effects. Plus, a recent scientific review published in The Lancet found an association between eating extremely high- or low-carb and mortality.

Alex Silver Fagan, a Nike master trainer, creator of Flow Into Strong, and coach at Performix House in NYC, knows that carbohydrates are an essential nutrient. Since the trainer lives for yoga and lifting, it basically goes without saying that she has to maintain a high level of energy at all times.

Silver Fagan, who holds a Precision Nutrition certification, argues that carbs are necessary since your body uses glucose derived from carbs as its main source of fuel. Not only can carbs help you power through workouts, but they're also important to basic mental function. Low carb diets have been linked to memory problems and slowed reaction times. "You need carbs to think, you need carbs to breathe, you need carbs to lift weights, you need carbs to drive a car," says Silver-Fagan. "You need carbs to just simply be a human, but people are cutting out carbs because it's the quickest way to elicit fat loss." Often when people cut out carbs they initially experience what's referred to as the "keto flu" or "carb flu"—fatigue, lightheadedness, etc., which nutrition experts attribute to carb restriction. (Related: Everything You Need to Know About the Keto Flu)

A caveat: Not all carbs are created equal. "What I think you should be afraid of is processed carbs and processed food in general," says Silver-Fagan. "Anything that comes in a wrapper, anything that has been on a production line, is probably not the best choice for you." The key is to learn to differentiate simple carbs from complex carbs. Simple carbs, which are abundant in foods like candy and soda, get quickly broken down by the body, leading to a surge of energy and a crash. Foods containing complex carbs, like whole grains, vegetables, etc., provide more steady energy and are higher in fiber.

So while Silver Fagan doesn't condone going all out with processed foods, she's definitely not anti-carb. "Denying your body carbohydrates is like denying your body oxygen," she says. "You literally cannot function."