Refined carbs are carbohydrates that have been processed and stripped of most of their nutrients and fiber. They are also known as simple carbs or processed carbs. Refined carbs include mostly sugars and processed grains, such as white flour made from refined wheat. They are considered "empty" calories because they provide very few vitamins and minerals. Eating refined carbs is linked to a drastically increased risk of many diseases, including obesity, heart disease, and type 2 diabetes. Refined carbs are present in many foods, including white bread, white rice, pastries, sodas, snacks, pasta, sweets, breakfast cereals, and added sugars.

In contrast, complex, unrefined, or "good" carbs such as vegetables, whole grains, and naturally sweet fruit digest slower, resulting in stable blood sugar and less fat accumulation. Health organizations recommend that 45 to 65 percent of daily calories should come from carbohydrates, but the majority of these should be from complex, unrefined carbs rather than refined carbs.

Some common sources of refined carbs include white bread, white rice, and ultra-processed snacks, like potato chips and candy. Swapping out some refined carbs for unrefined versions can make a big difference in overall health.