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One Major Side Effect of Eating Carbs, Says Science

It's a good thing—but you have to choose the right carbs to reap the benefits.
FACT CHECKED BY Olivia Tarantino
simple carbs

If there's ever been a time when we've cranked the pizza, pasta, and cookies dial way up, it's been this past year. Carbs, carbs, carbs, how we love and hate thee.

Looking beyond our love/hate relationship, we need to recognize that carbs are a crucial component of a healthy diet and a healthy body: "Carbohydrates are one of the three macronutrients we need to fuel the body. Carbs are actually the body's preferred source of energy," says Breanna Woods, MS, RD, co-creator of Blogilates 90 Day Journey Meal Plan.

But as we know, not all carbs are created equal. Whether you crash and burn after a meal or feel ready to put the pedal to the metal on your spiffy new stationary bike, has a lot to do with the kind of carbs you eat. In fact, one major side effect of carbs is getting the energy your body needs—but how much energy and how long that energy lasts all depends on the type of carb you're eating. You see, depending on the type of carb you choose to eat, the rate of your body's energy metabolism (that's science-speak for how your body breaks down food into fuel) will differ—either giving you lasting energy or a quick crash. (Related: 15 Carbs Myths That Are Totally Bogus)

As Woods explains, carbs from a candy bar and carbs from a sweet potato all share the same fate in our digestive tract—they are converted into glucose. Once that happens, cells in your body use that glucose to give you energy. "However, carbs are processed differently on their journey to becoming glucose depending on the kind you eat," she says. "Refined carbs like candy, white flour, and added sugar are broken down and absorbed quickly. This suddenly dumps glucose into the bloodstream all at once, which leads to a burst of energy now, but then a crash later," she continues, noting that you'll feel tired and hungry sooner rather than later.

On the flip side of the coin are complex carbs, which include wholesome eats like legumes, starchy vegetables, and whole grains. These food groups digest slowly, which is a boon for your energy levels (for more on complex carbs, check out the 24 best healthy carbs to eat for weight loss. "This means that glucose is absorbed into the blood at a slow and steady rate over a longer period of time with no spike in blood sugar meaning you avoid a crash later. Your energy levels remain steady, and you stay satisfied for longer between meals," says Woods.

And choosing complex carbs is more important than simply helping to power up your Monday morning workday or when you've hit an afternoon slump between lectures: "Steady glucose control is important for long term health too. Every time glucose enters the blood, the pancreas releases insulin to help glucose get into the cells. If your glucose levels are constantly spiking, the cells can become less sensitive to insulin. This leads to issues like inflammation, diabetes, and cardiovascular disease," cautions Woods, pointing to this 2018 study in Metabolism that followed 14 middle-aged adults, and found intake of whole grains (i.e., complex carbs) significantly improved post-meal glucose levels, compared with a refined grain diet.

(If you're not sure if you're eating too much sugar in your diet, consult this handy guide.)

It gets worse in the simple carbs camp: "A 2021 study published in the British Medical Journal followed over 137,000 participants from 21 countries to explore the connection between intake of refined grains and heart disease," comments Woods, adding that this research concluded that a high intake of refined grains increases the risk for major cardiovascular events, as well as total mortality. Hmmm…we think we'll pass and stick to complex carbs, folks.

In addition to enhancing your energy, complex carbs provide nutrients like fiber, vitamins, and minerals—all of which are stripped from refined carbs, says Woods. Fiber, in particular, is a key player in your overall health: "It's a nutrient most Americans are lacking, and facilitates slow digestion to create a steady energy source," says Woods. "Studies also show that fiber from complex carbs decreases risk for type 2 diabetes, cardiovascular disease, and cancer." We'll replace that pizza, pasta, and cookies, with this triple win against disease any day of the week! And if you're not sure if you should be adding fiber to your diet, check out these 9 Warning Signs You're Not Eating Enough Fiber.

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Perri O. Blumberg
Perri O. Blumberg is a freelance food, health, and lifestyle writer. Read more
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