Carbohydrates are molecules, and all of them are composed by carbon, oxygen and water. The difference lies within their chemical structure which gives them a wide variety of properties, such as digestion difficulty (time) and sweetness. Although they are made by the same molecules, there are different types of carbohydrates classified as follows:
Simple carbohydrates are also known as simple sugars, and are made by one (monosaccharides) or two sugar molecules (disaccharides). These types of carbohydrates contain all the flavor (sweetness) with poor nutrition. Also, since they have the simplest molecule structure, they’re the first to be metabolized by your body, and the quickest source of energy. This is why people who perform in high intensity sports or explosive activities tend to eat them prior to their training.
Some examples of these carbohydrates are: Glucose, fructose and lactose. And some foods which contain them are: milk, fruit juice, sugar, honey, candies, etc.
Complex carbohydrates are made by three or more sugar molecules (polysaccharides). These carbohydrates do not necessarily taste sweet, despite them being composed by sugar molecules. The nourishment provided by these types of carbs ranges from almost nonexistent to a nutrient dense level. Also, due to their chemical structure, the release of energy from these carbs takes longer time. This might be the reason why people who are preparing for a marathon, or a long competition ingest a lot of them.
Examples of these types of carbohydrates are: starch and fiber. Foods considered as complex carbohydrates are: pasta, rice, potatoes, vegetables, bread, etc.
All the foods considered as complex carbohydrates contain sugar, starch and fiber, however the amount varies, therefore we can split them into groups:
Poor nutrition, poor fiber content and moderate-high amount of starch:
- White bread
- White rice
These foods are commonly used purely as an energy resource.
Some nutrition, some fiber, some starch:
These are used for energy and nutrition.
A lot of nutrition, a lot of fiber, very little starch-nonexistent starch:
These carbohydrates are used mainly for nutrition purposes due to its high micronutrient content.
Fiber deserves at least a paragraph on its own. Because there are two types of fiber, soluble fiber, which is slowly digested by your body, and slowing the digestion of other foods. And insoluble fiber, which is not digested by your body but helps with the feeling of satiety. Sometimes on a low carb diet or a ketogenic diet you will hear about Net carbs. Net carbs means the total amount of carbohydrates minus the fiber.
TIP: Only count net carbs if you know its insoluble fiber, preferably on cruciferous vegetables.
How does this applies to a ketogenic diet?
Simple, on a ketogenic diet you get your energy from FATS, therefore you don’t need to worry about getting your energy from carbohydrates. Your only worry about carbohydrates should be nutrition. This means you are not supposed to eat any other complex carbohydrate but vegetables, and absolutely none of the simple carbohydrates. In fact, simple carbohydrates will make your body metabolize them first despite your state of ketosis.
Finally here’s a video on the topic.