The difference between complex and simple carbs — and 5 health benefits of opting for complex carbs

• Complex carbs have lots of sugar molecules bonded together in long chains and take longer to digest.
• Whereas simple carbs have just one or two molecules that your body absorbs quickly.
• Since complex carbs are harder to digest, they keep you full for longer and contain more nutrients.
• Visit Insider's Health Reference library for more advice.

A lot of diets will tell you to cut carbs, but not all carbs are unhealthy. Carbs actually fall into two categories: complex and simple. 

• Complex carbs, like whole grains, have important health benefits because they're high in nutritious starches and fiber. 
• Simple carbs like table sugar don't offer the same nutrients and may be harmful to your health if you have too much.

Here's why complex carbs are part of a healthy diet and some tasty ways to eat them.

Complex carbs vs. simple carbs

"Carbohydrates are the body's main source of energy," says Karen Ansel, MS, a registered dietician in private practice. 

Your body breaks carbohydrates down into glucose, which is absorbed into your bloodstream, and provides energy for your muscles, organs, and brain.

But your body breaks down carbohydrates differently depending on whether they're simple or complex.

Simple carbohydrates 

"Sugars are considered simple because they are simple in structure, consisting of just one or two sugar molecules," says Charlotte Martin, MS, a registered dietician with a private practice. 

Because of this simple structure, your body can break them down quickly. This quick breakdown also allows them to be absorbed quickly — which can lead to blood sugar spikes that can be dangerous for people with diabetes and prediabetes. 

Simple sugars can be naturally occuring, like the fructose in fruit. But some simple carbs are made from complex carbs that are broken down to a simpler structure during the refining process. 

This process removes parts of the plant that contain fiber, starches, and other nutrients. For example, refined white flour is made by removing the fibrous bran and starchy endosperm before grinding the wheat. 

Complex carbohydrates 

"Starches and fiber are considered complex because they are often made up of hundreds or even thousands of sugar molecules bonded together into long, complex chains," Martin says.

Complex carbs like starches and fiber take longer to digest because of their more complex structure, Martin says. This causes your blood sugar to rise mouch more slowly and may improve your gut health.

Examples of complex carbs

"The foods we think of when referring to 'complex carbs' are typically those that are less refined and processed and therefore retain their fiber," Martin says. These foods include:

• Whole grains, including:
• Brown rice
• Oatmeal
• Whole wheat bread
• Quinoa
• Legumes like:
• Beans
• Lentils
• Split peas
• Chickpeas
• Vegetables like:
• Carrots
• Zucchini
• Sweet potatoes
• White potatoes with the skin 

Benefits of complex carbs

Complex carbohydrates have several important health benefits that you can't get from simple carbs.

1. They keep your energy levels steady. Because complex carbs retain their fiber, they are digested slowly and gradually release glucose into your bloodstream. This provides a more steady supply of energy, rather than a blood sugar spike and subsequent crash, which will leave you feeling drained and fatigued, Martin says.
2. They're packed with key nutrients. Complex carbohydrates tend to have more vitamins, minerals, and phytonutrients than simple carbs because the refining process to make simple carbs often stripps away those nutrients, Martin says.
3. They make you feel more full which can help with weight management and weight loss. "Because dismantling complex carbs takes time, they are really great for helping you stay full between meals," Karen Ansel says. This may help cut down on snacking and taking in excess calories. Studies show that the fibers found in oats and beans both trigger feelings of fullness.
4. They keep your blood sugar in balance. Because you digest complex carbs more slowly, they can also help you avoid spikes in blood sugar that can come from highly processed, refined carbohydrates, Ansel says. This is especially important for people with diabetes. A 2020 review of 42 studies found that diabetics who eat a high-fiber diet have more stable blood sugar than those who eat a lower fiber diet.
5. They're good for your gut. "Certain fibers known as prebiotics act as fuel for your good gut bacteria," Martin says. Having plentiful gut bacteria is important for your health — it can help you avoid digestive issues and fight off harmful bacteria.

Insider's takeaway

Choosing fiber-rich, complex carbs like whole grains over refined carbs is one of the best ways to support your health. Complex carbs are rich in nutrients and help you avoid sugar spikes and crashes.

But it's okay to have an occasional treat — "a slice of chocolate cake on date night or a meal at home with white spaghetti rather than whole-wheat pasta won't ruin your health," Martin says.