Carbs can be confusing. Some weight-loss pros swear that they make you hungrier—and heavier. Others insist they’re the foundation of a healthy diet. That makes it hard to know what to believe. But before you ditch pasta, bread, and potatoes, read this.
“Carbohydrates are nutrients that provide quick, easy energy for your muscles and brain, making them your body’s favorite source of fuel,” says Sylvia Klinger, RD, a nutritionist based in Hinsdale, Illinois. Carbs are essentially made up of sugar molecules in different combinations. After you eat a carb-containing meal or snack, its carbohydrates travel to your small intestine where they’re absorbed into your bloodstream. From there they travel to your liver, where they’re converted to your body’s favorite source of energy, glucose, to feed body cells. Some glucose can be stored in the liver or muscles as glycogen and then released into the bloodstream whenever your body needs energy. If energy is supplied in amounts greater than the body needs, excess glucose can be converted to fat.
While you may have known that carbs give your muscles the fuel they need to power through physical activities, you may not have realized that your brain runs on carbs, too, burning through roughly a quarter of your body’s energy every day. Carbohydrates have another important job, too: They may also help increase the release of the feel-good brain chemical serotonin that helps melt away stress and anxiety.
Good Carbs, Bad Carbs?
If carbohydrates are so great for you, why do they get such a bad rap? “People tend to eat carbohydrates in the wrong amount and the wrong balance,” says Julie Miller Jones, PhD, CNS, a professor emerita of nutrition at St. Catherine University in St. Paul, Minnesota. “We live in a world where restaurants may serve the equivalent of six servings of pasta in an unlimited pasta bowl, or a bagel, which delivers three or more servings of bread.”
What’s more, not all carbs are created equal. There are essentially three kinds of carbohydrates: Simple carbs, complex carbs, and fiber.
Simple carbohydrates, as mentioned above, are made of single or double units of sugar. These require little to no digestion. Single sugars, like fructose from fruit, are absorbed directly into the small intestine, while double sugars, such as table sugar (aka sucrose) or milk sugar (lactose), are split into simple sugars by special enzymes that reside in the gut and then quickly absorbed.
Complex carbs are on the opposite end of the spectrum, consisting of longer chains of sugar, or starch. Because these are much harder to digest, your saliva contains enzymes that begin to break them down as you chew your food. But the small intestine is where the real work happens. There, a special enzyme called pancreatic amylase chips away at those long, stubborn chains of starch, slowly breaking them into simple sugars. While they eventually enter the bloodstream as sugars, the process of dismantling them takes more time so that they provide sustained energy in comparison to the quick flood of sugar that you get from simple carbs.
Fiber is a carbohydrate found only in plant foods naturally. Because your body lacks the enzymes to break it down, it passes right through your system without ever being digested.
Sometimes Simple Isn’t Better
Recently sugar—which is really a pseudonym for simple carbs—has been getting slammed for potentially causing everything from unwanted weight gain to type 2 diabetes. However, nutritionally speaking, not all sugar-containing foods are the same.
Sugar can be added to foods or is just a natural part of a food’s makeup. Added sugar is found primarily in soda, candy, cupcakes, and the like, but natural sugar often comes with an array of nutrients and fiber in foods like fruit, juice, and milk. Sugar promotes the release of insulin into the blood. Eat a little bit and your body is feeding your muscles and brain the way it was designed; eat more than you need and leftover excess sugar is stored as fat. If this happens once in a while, it’s no big deal. But when it becomes the norm, pounds can easily sneak up on you.
What about natural sugar?
If too much added sugar makes you hungrier, you might be wondering if you should avoid foods that contain natural sugars like fruit and milk. The answer is a resounding no! The sugars in these foods exist in combination with other nutrients (such as protein and vitamins) and beneficial phytochemical and antioxidants that can modulate their effect.
Just compare 8 ounces of milk to 8 ounces of soda. The milk supplies 13 grams of sugar. In return, you get nearly a third of your day’s calcium, a fifth of the daily value for vitamin D, and 8 grams of high-quality protein. The soda, by comparison, packs 26 grams of carbs and zero nutrition. And that’s for a tiny 8-ounce cup, which is a lot less than most people drink. What’s more, natural sugars often occur in a matrix of fiber, which slows down their absorption. So even though fruit delivers anywhere from 7 sugar grams in a cup of strawberries to 19 grams in a medium apple, because the sugar in these pieces of fruit is packaged in a matrix of fiber, it doesn’t overwhelm your system the same way a couple of cookies would, and you may feel more satisfied.
The Complex Carb
Unlike most simple carbs, complex carbohydrates are your friends, thanks to their prolonged energy release. You can find them naturally in whole foods like beans, whole grains, and vegetables.
In addition, “These foods provide an A to Z mix of naturally occurring plant nutrients called phytonutrients, which are credited with fighting diseases like heart disease and cancer,” says Susan Mitchell, PhD, RDN, producer of the podcast Breaking Down Nutrition.
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Fiber: the Forgotten Carb
Then there’s fiber, potentially one of the most underrated carbs out there. Sure, it keeps your digestive system running smoothly, but that’s just the beginning. “There are many kinds of fiber, each with unique and wonderful health benefits,” says Jones. “We should really be treating fiber the same way we do vitamins, striving to include lots of different types in our diets every day.” Case in point: The beta-glucan fiber in oats and barley helps reduce cholesterol, while the soluble fibers in beans may better help control blood-sugar levels. There are even fibers in corn and inulin that can help you absorb more calcium and magnesium.
Because fiber, aka roughage, can expand in your gut like a sponge in some cases, it may have an impact on appetite by helping you feel full faster, by taking more room in your stomach, and by taking longer to chew. And over the long term, it encourages the growth of good gut bacteria believed to influence hormones that help regulate appetite, says Jones. If you need convincing, consider this: People who ate about 25 grams of fiber each day for a year lost 4½ pounds overall, according to a clinical trial of 240 people with metabolic syndrome that was reported in the Annals of Internal Medicine.
If 25 grams sounds like a tall order, try working fiber-rich foods like beans, fruits, and vegetables into every meal and snack. Those fiber grams will start to add up before you know it.
Making Carbs Work for You
So far from being the enemy, carbs are a potential ally. Most weight-loss experts agree that they can safely make up anywhere between 45 percent to 65 percent of your daily calories. “In the end, it can be hard not to get swept up in the frenzy of carb confusion,” says Klinger. “But the truth is, as long as you don’t go over your carb recommendations they can still be a healthy part of your weight-loss plan.”
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