Everything you want to know about carbohydrates, explained

Dec. 2, 2018 / 5:41 PM GMT

By Samantha Cassetty, RD

Love ‘em or hate ‘em, carbs are completely misunderstood. Carbs (short for carbohydrates) are one of the three macros (short for macronutrients); protein and fat are the remaining two. Once eaten, carbohydrates get broken down to sugar, or glucose, in your blood, and from there, the glucose from carbs supplies energy to every cell in your body. Notably, your brain demands the most energy, and it’s said that your neurons —basically, your brain’s messengers — need a steady supply. Since carbs remain a mystery to many, here are answers to the most common questions about this food group.

Which foods contain carbs?

It’s probably no mystery that bagels and pasta are considered carbs, but there are plenty of other foods that fall in the carb camp. They are:

• Grains. This means you’ll find carbs in both refined grains (such as white bread and white rice) as well as whole grains (including quinoa, whole wheat and oats).
• Vegetables. Some, like broccoli and leafy greens, have very few carbs, while starchy veggies, such as white and sweet potatoes and corn (often considered a grain) have more.
• Beans. Foods like lentils, chickpeas, black beans, and soybeans supply carbs.
• Fruits. All forms of fruit, whether frozen, fresh, dried or juiced have carbs.
• Dairy. Milk, yogurt, and cottage cheese have varying amounts of this macro.
• Sweets. Lots of foods — from ice cream to cookies — fall under this category, and anything that has sugar has carbs.

Other foods provide carbs but in lower amounts. And some of the foods listed here supply other macros. For example, yogurt and beans are both sources of carbs and protein. If you’re choosing whole milk yogurt, it’s also a source of fat.

What’s the difference between simple and complex carbs?

Simple carbs are broken down into glucose quickly. Perhaps you’ve experienced a sugar rush — aptly named because the sugar breaks down easily to supply that instant energy. Examples of simple carbs include fruit juice, which is stripped of fiber, and all forms of sugar, whether natural, like maple syrup and honey, or more processed table sugar. Your body isn’t picky here; it will convert them all to sugar quickly. By providing this instant energy, simple carbs cause a faster rise in blood glucose, which prompts your body to produce insulin in response.

The term complex carbs refers to the chemical structure of carbs, and this is where things get a little tricky. Complex carbs can include foods, like fruits and whole grains, which have fiber as well as other nutrients, and the term can also include chemically complex carbs, like white bread, which has little to no fiber or nutrients that occur naturally.

Is this the same as good carbs and bad carbs?

No. When you hear the term good carbs, it usually refers to whole food carbs that have vitamins, minerals, and protective plant substances. Many good carbs also provide fiber. These are key distinctions because these carbs tend to be digested more slowly — whether because they also have protein (in the case of milk and yogurt, for instance), or because they have fiber (think: sweet potatoes or beans). This slower conversion to glucose means your body has a steadier stream of energy, and it doesn’t cause as many drastic fluctuations in insulin that can be problematic. Taken together, the protective compounds and healthier insulin response puts these types of foods in the good carb camp.

Typically, foods that have excessive sugar and refined grains are considered bad carbs because they supply few, if any, nutrients (including fiber), and their fast conversion to energy prompts unhealthy fluctuations in insulin levels. Over time, this can tax your system and lead to insulin resistance and type 2 diabetes.

One side note here: Refined grains are stripped of their nutrients during processing, but many are enriched (as indicated by the term “enriched wheat flour”), meaning that certain nutrients have been added back in. That means they supply some B vitamins, including folic acid, as well as iron. Because these nutrients are important, the USDA allows for making half your grains whole and the other half can come from these processed grains. However, the truth is, you’re better off limiting your consumption of refined grains and choosing other whole foods rich in those same nutrients. That’s a little off topic for a carb conversation but worth mentioning in the context of good and bad carbs since processed grains do have a few added nutrients.

So this means some carbs are healthier than others?

Yes! I know people get up in arms about calling food bad, but in the interest of science, some foods are plainly better for you than others, and this is certainly true of carbs. Take fruit. Fruit has fiber, vitamins, minerals, and antioxidants that protect our cells from damage caused by aging, invaders or the environment. In addition to defending your body against diseases, increasing fruit and veggie consumption can also up your happiness-meter. One study looking at more than 12,000 adults over the span of six years found that happiness increased with increasing servings — leveling off at eight servings per day (though you’ll benefit from less).

Beans, also rich in carbs, provide protein, fiber, calcium, iron, folate, magnesium, zinc, and other nutrients. And of course, the fiber in good carbs helps feed the trillions of bacteria in your gut, creating a diverse ecosystem that strengthens your immune system and protects you from certain diseases.

The science is very clear on this: Whole food carbs offer health benefits, whereas refined and processed carbs have a negative impact on your weight and health.

How many carbs should you eat in a day?

This can vary widely depending on the person, lifestyle factors (say, daily killer workouts compared to a desk job with little activity), and goals. A healthy dietary pattern includes mostly good carbs in right-size portions spread throughout the day. Since portions are typically smaller than people think — for instance, ½ cup of whole wheat pasta or brown rice, or a slice of bread — I find that it’s pretty common to have portion problems with starches, a scenario that often means your veggies are being displaced. I recommend reversing the ratio instead so your veggie portion is the largest and the starchy carb portion is much smaller. This is an easy way to think of it so you don’t have to count, measure, weigh or track anything!

Is it better to go on a low carb diet for weight loss?

I always lean on science to answer this question, and it points to the fact that there is no best way to lose weight. It all comes down to what’s sustainable for you. There’s a common thread among popular diet programs: eat whole foods over processed ones, curtail your added sugar intake, and eat more veggies. It’s always a good idea to work with a registered dietitian or look for a plan that has these main pillars and fits within your lifestyle.

What’s the deal with net carbs?

When people are tracking their carb intake, they often subtract the amount of fiber from the total carbs in a given food. That’s because fiber, while technically a carb, isn’t digestible, so it doesn’t cause the rise in blood sugar that other carbs trigger. If you’re not tracking your carb intake, and your carbs are mostly whole foods (i.e., good carbs), you don’t need to think about net carbs.

What does gluten have to do with carbs?

Gluten is a protein (yes! A protein!) found in wheat (a carb). Going on a low carb diet does not mean you’ll be excluding gluten and going on a gluten free diet doesn’t mean you’ll be nixing carbs. Plenty of healthy carbs, like fruits, starchy veggies, beans, yogurt, and even some grains, like buckwheat (confusing, I know) and quinoa are gluten free. If you don’t have celiac disease or gluten sensitivity, there’s no need to steer clear.

WHAT A NUTRITIONIST WANTS YOU TO KNOW

Want more tips like these? NBC News BETTER is obsessed with finding easier, healthier and smarter ways to live. Sign up for our newsletter and follow us on Facebook, Twitter and Instagram.