A Dietitian’s Take: Cutting Carbs for Weight Loss

by Sasha Reddy

This article has been reviewed by Jeannie Versagli, RD, LDN. Jeannie is a Registered Dietitian with the Academy of Nutrition and Dietetics, a national professional organization, and is licensed in nutrition with the State of Delaware.

If I had a nickel for every time I’ve read a blog post or heard an online influencer preaching the power of cutting carbs for weight loss, I could probably buy my weight in gold. How have carbohydrates, one of the pillars of the modern food pyramid, earned such a bad rap? Are they really the culprits of unwanted weight gain they’re made out to be?

“‘Carbs’ has become a bad word today in nutrition for most non-professionals,” says Jeannie Versagli, one of HAC’s Registered Dietitians licensed through the State of Delaware. For years, she’s observed the spread of misconceptions around carbohydrates fueled by flashy headlines and fad diet culture. In reality, carbs are the body’s primary fuel source and a necessary part of a healthy diet.

“By just arbitrarily saying that you are going to cut out carbohydrates, you are putting your body at a significant deficit,” Jeannie notes. Significantly or entirely reducing your carb intake means you are likely not 1) providing your body with enough fuel and 2) consuming all the vitamins and minerals your body needs to function well. Let’s break that down.

Types of Carbs

First and foremost, let’s review the two different types of carbohydrates: simple and complex. Simple carbs, also known as simple sugars, break down and release glucose in your body very quickly. While simple sugars are commonly found in processed foods, they also occur naturally in fruit and milk. Complex carbohydrates are broken down slower, providing a more constant energy source. Legumes, starchy vegetables, and whole grains all contain complex carbs.

“The body functions off of glucose,” Jeannie says. “It’s the gas for the engine.” Though both forms of carbs contain glucose (also known as sugar and not as scary as you may think), complex carbs provide a more sustained source of energy, making them more desirable.

So, does that mean it’s okay to ditch all simple carbs? Not quite. Processed foods that contain simple sugars often cause inflammation, offer little to no fiber, and include unnecessary added sugars. “By taking those in, whether you have weight gain or not, oftentimes you’re causing inflammation,” Jeannie says. However, fruits offer our bodies fiber and other nutrients that contribute to a balanced diet and should not be omitted.

Energy Efficiency

As we previously noted, carbs are the body’s primary fuel source. “Carbohydrates require very little breakdown in the body to be utilized,” Jeannie says. “All the other foods that we take in require significant extra steps to be broken down for the body to use for energy.” Think about this in the context of exercise. The more you exert yourself, the higher your heart rate jumps and the more calories you burn. However, the ratio of calories burned from fats vs. calories burned from carbs changes, too.

Simply put, our bodies are only able to burn fat during low to moderate-intensity exercise; the higher your heart rate, the lower your body’s ability to burn fat. When you are working at a moderate intensity (below around 70% of your max heart rate), your body is burning a mix of calories from fats and from carbs. But once your heart rate reaches between 70-80% of your max heart rate, your fuel source begins to switch from fat to muscle glycogen and glucose (100 percent of your calories burned are calories from carbs). So, if you are running on a carb deficit, your body starts to use muscle for fuel because it can’t just switch to burning fat – as Jeannie describes, “the body can’t physiologically break down fat at that high-intensity VO2 max.” Instead, you end up running out of energy, leaving your body unable to function to its full potential and likely cannibalizing your hard-earned lean body mass in an attempt to convert protein to the carbohydrates your body so desperately needs. Certainly counterproductive!

All of these foods consist primarily of carbohydates!
Nutrient Considerations

Carbs are also some of our most prominent sources of fiber and B vitamins, so it goes without saying that by cutting carbs out of your diet, you will be depriving your body of these and other important nutrients.

Fiber Fiber is primarily found in plants: fruits, vegetables, whole grains, beans, etc. The two types of fiber – soluble and insoluble – benefit us in different ways. Soluble fiber helps regulate glucose and cholesterol levels. Insoluble fiber digests at a slow rate, keeping you satiated for longer, and it’s one of the best contributors to digestive health. “Fiber is critical for microbiomes, critical for managing glucose, and critical for managing cholesterol,” Jeannie emphasizes.

B Vitamins – B Vitamins are essential nutrients that serve our bodies in countless ways, working on a cellular level to ensure that all parts of our bodies are working properly. Some of the areas in which B vitamins benefit us include mental health, immune system function, nervous system function, and dementia and stroke prevention.

Addressing the Real Problem

The issue with carbs and weight loss isn’t so much about carbs themselves – it’s about how they are used. When carbs aren’t quickly burned for energy, they are converted into glycogen. And when the body has produced all of the glycogen it can store, it begins turning any remaining glucose into fat. So, while it is important to avoid consuming more carbohydrates than your body needs, cutting carbs isn’t always the right solution.

It’s pretty much impossible to entirely cut carbs from our diets anyway. “Fruits, vegetables, and grains are all carbohydrates.” Jeannie reiterates. “A little bit of proteins, too. Dairy, same thing. There’s no one particular food group that gives you everything. People do themselves a terrible disservice when they aren’t wise about their choice of fuel for their body.” As with any nutrition dilemma, eating a well-balanced, nutrient-dense diet alongside an active lifestyle is the best approach to losing weight.

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