Fast-digesting carbs may also be called fast acting carbs, and they are almost always carbohydrates that are primarily composed of simple sugars rather than a balance of macronutrients (fats and proteins).
But, how do quick digesting carbs differ from other types of carbs, and when should you eat them?
In this article, we will discuss what fast digesting carbs are, the pros and cons of eating them, and give you a list of fast digesting carbs and easy to digest carbs for times when you need a quick boost of energy.
We will cover the following:
- What Are Fast Digesting Carbs?
- How Do Fast Digesting Carbs Work?
- Are Fast Digesting Carbs Bad For You?
- Examples of Fast Digesting Carbs
Let’s dive in!
What Are Fast Digesting Carbs?
As the term describes, fast digesting carbs are carbohydrates that are quickly digested and absorbed into the bloodstream shortly after you ingest them.
For this reason, fast digesting carbs are often called quick digesting carbs or easy to digest carbs because the time course after ingestion, until the sugars from the carbs hit your bloodstream, is relatively brief, and the digestive process is simple and generally free from distressing symptoms like bloating, gas, or nausea.
Fast digesting carbs are often called simple carbohydrates or simple sugars because they do not contain long carbohydrate molecules called polysaccharides.
When many smaller sugar molecules link together and form polysaccharides, such as in starches, it takes longer to break down the molecules, causing a slower release of glucose into the bloodstream.
How Do Fast Digesting Carbs Work
Simple sugars are smaller sugar molecules, such as the monosaccharides glucose, galactose, and fructose, or disaccharides such as sucrose and lactose.
Fast acting carbs are also very low in fiber or contain no fiber, and the carbohydrate molecules themselves are mainly monosaccharides and disaccharides, which are simple sugars.
The reason that fast digesting carbs do not contain fiber, such as cellulose or inulin, and do not contain particularly long polysaccharide chains of carbohydrates, such as starch, is that fibrous carbs and starchy carbs take longer to break down.
Fiber slows digestion because it is not readily broken down or absorbed, and the longer polysaccharide molecules, which are long chains of mini simple sugars strung together, also take a longer time to break down and digest, slowing the release of sugar into the bloodstream.
In contrast, simple sugars, or fast-acting carbs, are already nearly in the state ready to be absorbed into the bloodstream.
For this reason, fast-acting carbs are considered high-glycemic foods or those that rank high on the glycemic index. The glycemic index (GI) is a measure of how fast your body converts carbs into sugars that can be absorbed into your bloodstream.
The glycemic index score of a food ranges from 0 to 100, with the categories of “low glycemic foods“ having a glycemic index value of 55 or less, “medium glycemic index foods“ having a score of 56 to 69, and “high glycemic index foods” having a glycemic index value of 70 to 100.
Low-glycemic foods also tend to contain fiber, such as cellulose and inulin, which are plant-based components that the body cannot readily absorb or digest. These foods take longer to break down, causing a slower release of glucose into the bloodstream.
The simple sugars in fast digesting carbs may only involve one or two steps to further break them down to glucose to be released into the bloodstream, which means that the digestion and absorption are rapid after ingestion.
Therefore, fast digesting carbs are both fast-acting carbs and easy to digest carbs. For this reason, when you eat simple sugars or quick-acting carbs, the sugars will give you a quick boost in your blood sugar soon after eating them.
However, because fast-acting carbs are mainly simple carbohydrates without containing much protein, fat, or fiber, the blood sugar spike, and the resultant insulin spike are both high.
Are Fast Digesting Carbs Bad For You?
From a health standpoint, it is often not advisable to eat foods high in simple sugars or to consume a diet rich in fast digesting carbs.
When you regularly consume a lot of simple carbs, your blood sugar levels are chronically getting elevated, and insulin is being secreted and circulated frequently and at high levels.
This can increase the risk of developing insulin resistance over time, in which your cells are no longer as sensitive to this hormone.
The body will have to keep producing more and more insulin in order for your cells to recognize that there is blood sugar present in the bloodstream that they can take up and use.
Insulin resistance can eventually lead to type 2 diabetes, obesity, and metabolic syndrome.
However, there are certain circumstances where it is actually ideal to choose high carb foods that are primarily composed of simple sugars to capitalize on the energy boost and the digestive simplicity of eating them.
For example, if you are heading out for a run or trying to have a pre-workout snack but do not have much time to digest your food before you exercise, choosing simple carbs and easy to digest carbohydrates is often the way to go.
Similarly, fast digesting carbs are ideal for fueling during a workout, such as during a long run training for a marathon, on the bike when doing a triathlon, or even at the gym lifting weights for a high-intensity resistance training workout.
In each of these scenarios, you want to capitalize on fast-acting carbs to keep your blood sugar high enough so that there is ample blood glucose circulating for your muscles to take up and use for energy without needing to deplete and break down all of your glycogen, which requires another step and is a limited resource.
Moreover, simple carbohydrates are easy-to-digest carbs, reducing the risk of digestive distress when you are exercising at a high intensity.
Some runners and endurance athletes prefer to run on an empty stomach because they struggle with digestive symptoms such as side stitches, cramps, bloating, nausea, gas, or diarrhea if they run too soon after eating.
However, depending on your own personal metabolism, diet, weight goals, training intensity, and training status, you may find that running or working out on an empty stomach compromises the quality of your workouts as well as how you feel.
This is due to the fact that carbohydrates are the muscles’ preferred fuel source during high-intensity exercise, but the body only has limited carbohydrate stores.
According to the Academy of Nutrition and Dietetics, an endurance-trained athlete can store up to 1,800 to 2,000 calories of fuel as glycogen in the muscles and liver, though smaller runners might store closer to 1,500 calories.
Choosing fast-digesting carbs right before and during endurance workouts can help ensure the foods and drinks pass through the stomach quickly so that the sugars reach your bloodstream for use without weighing you down while you try to work out.
Examples of Fast Digesting Carbs
Here is a list of some examples of simple carbs that are digested and absorbed rapidly into the bloodstream:
- Gatorade and sports drinks
- Jelly beans, gum drops
- Fruit juice, lemonade, soda pop
- White bread
- Grapes, papaya, oranges, figs, plums, peaches, nectarines, apples, pears, plantains, watermelon, bananas, dried fruits, pineapple, mango
- Sweet Potatoes
- Chex cereal and Chex mix
- Breakfast bars with jam in the middle
- Jelly and jam
- Graham crackers, white crackers like saltines, cookies, meringue cookies, pretzels
- Lollipops and jolly ranchers
- Baby food fruit pouches like plum purée, banana purée, and apple purée
- Fruit cocktail cups
- Energy gels
- White bread, white rice, white tortillas
- Honey, maple syrup
- Sherbet, popsicles
- Fruit roll-ups and fruit snacks, Gushers
- Lifesavers, Tootsie Rolls, Swedish fish, Sour Patch Kids
- Rice crispy treats
- Granola bars like Quaker Chewy granola bars
- Yogurt-covered raisins
- Mashed potatoes
- Glazed donuts, basic cake donuts, donut holes
- Muffins other than bran muffins or those baked with whole wheat flour, oats, and nuts
- Pop-tarts and toaster pastries
- Rice cakes, especially sweetened rice cakes like caramel rice cakes
- White bagels, cinnamon sugar bagels, cinnamon raisin bagels, blueberry bagels, and most bagels other than whole wheat or brand bagels, particularly if there is no topping on the bagel
- Quick oats oatmeal
- Sugary breakfast cereals such as Lucky Charms, Frosted Flakes, Fruit Loops, Kix, Trix, Coco Pops
- Croissants, danishes, pastries
- Fruit pies like blueberry pie, apple pie, sweet potato pie, cherry pie
- Low-fat ice cream
- Sugar-sweetened yogurt, especially if they are fat-free and non-Greek yogurts, Go-Gurt
To learn more about ideal carbohydrates to help fuel endurance exercise, check out our guide to natural alternatives to energy gels here.