As a Dietitian, it’s my job to educate clients on how to incorporate fast-digesting carbs into their diet, which can be a game changer for those looking to improve their sports performance.
The biggest barrier that clients mention is figuring out which carbs are fast-digesting.
Some examples of fast-digesting carbs include watermelon, white bread, fruit juices, sweets, honey, Gatorade, sports gels, and soda. These foods consist of simple and refined carbs, so they provide the body with energy at a faster rate compared to slower-digesting carbs, which take longer to break down.
Knowing the type of carbohydrate foods to choose when you need to counteract low energy (low blood sugar levels) or promote a faster recovery after exercise is important.
Below is a complete list of fast-digesting carbs for you to reference.
- Fast-digesting carbs refer to high glycemic foods, which convert into glucose (energy) within about 15-30 minutes after consumption.
- The rate at which fast-digesting carbs convert to energy will depend on the type of sugar and whether it is consumed on its own or with foods containing protein and/or fat.
- The best time to have fast-digesting carbs is when you are feeling low on energy before/during a workout, or after a workout to promote recovery.
What Are Fast Digesting Carbs?
Some carbs are known to digest (break down and absorb) faster than others.
The rate at which carbs digest affects how they impact your blood sugar levels and how energized you feel.
To help understand this, the glycaemic index (GI) tool is often used to rate carbs based on how quickly they affect blood sugar levels (on a scale from 1 to 100).
Fast-digesting carbs refer to carbohydrates that provide immediate energy. This is because they are broken down and absorbed by the body as energy (glucose) more quickly, causing a faster increase in blood sugar levels.
On the other hand, slow-digesting carbs refer to carbohydrates that provide a more steady energy supply. This is because they are broken down and absorbed at a slower rate.
As such, they are referred to as low GI carbohydrates and do not spike blood sugar levels, leading to a slow and steady increase in blood sugar.
What Do Fast Digesting Carbs Do in the Body?
While fast-digesting carbs provide quick energy, they can also cause large spikes and drops in blood sugars.
To understand this and use them to your advantage, I’ll walk you through how these carbs are used in the body.
Once you ingest a fast-digesting carb (i.e. mango), your body will break it down into small sugar molecules.
The digestion of these sugar molecules starts in the mouth and continues through to the stomach.
From the stomach, these molecules will reach the small intestine, which is where all nutrient absorption happens.
Here, the sugar molecules enter the bloodstream as glucose, consequently increasing blood sugar levels.
The rise in sugar in the bloodstream will trigger the release of insulin, which signals your cells to use this sugar for energy.
At this point, with abundant insulin in circulation, different organs in the body (muscles, brain, liver, etc.) will take up glucose as energy. This means that blood sugar levels will fall rapidly.
This process happens quickly, which is why fast-digesting carbs are ideal for providing a quick burst of energy.
This burst of energy can be beneficial before or during intense exercise, or to quickly replenish energy stores after exercise.
- Related What Are Fast Digesting Foods?
How Quickly Do Fast Digesting Carbs Digest?
Fast-digesting carbs are rapidly broken down and absorbed into the bloodstream, which can take around 15-30 minutes, depending on the type of sugar molecule (monosaccharide, disaccharide, oligosaccharide, or polysaccharide) that is consumed and what is paired with.
Type Of Sugar Molecule
The simplest of carbs (monosaccharide), like glucose/dextrose or fructose (i.e. fruit juice), will likely take around 15 minutes because there are fewer molecules to break down, compared to a complex carb (polysaccharide).
If it’s a more complex carb, such as refined starches (i.e. bread), it will likely take a bit longer (around 30 minutes) as the body will take a bit longer to break it down.
If you mix carbs with other nutrients, such as protein and/or fat, it will slow down the digestion and absorption of carbs.
This is because fiber, protein, and fat all have slower rates of digestion, so they will influence how quickly food leaves the stomach.
This is why those who struggle with balancing their blood sugars are advised to pair protein and/or fat sources with their carbs.
20+ Fast Digesting Carbs
Some fast-digesting carbs are absorbed quicker than others, depending on the type of carb molecule that needs to be broken down (for example, whether it’s a monosaccharide or a polysaccharide).
Below is a list of fast-digesting carbs based on different food groups.
5 Fast Digesting Sugars
These carbs contain a mix of simple sugars:
- White table sugar (sucrose)
- Honey (fructose + glucose)
- maple syrup (sucrose)
- Agave syrup (fructose)
- Jam (fructose + sucrose)
5 Fast Digesting Fruits
These carbs contain mostly fructose and glucose:
- Ripe banana
4 Fast Digesting Sweetened Beverages
These drinks contain a mixture of added and natural sugars (sucrose, glucose, and fructose):
- Coca-cola (soda)
- Fruit juices
- Red bull (energy drinks)
4 Fast Digesting Refined Grains
These are refined starchy grains that have been processed to add sugars and remove fiber, and take 30+ minutes to absorb for most people:
4 Fast Digesting Sport Supplements
These contain a mixture of glucose/dextrose, sucrose, fructose, maltose, and/or maltodextrin:
When is the Best Time to Eat Fast Digesting Carbs?
The best time to eat fast-digesting carbs depends on your goals and exercise level. If you are an athlete or someone who does lots of exercise, consuming fast-digesting carbs before, during, and after exercise can be beneficial.
Eating fast-digesting carbs before/during exercise can provide quick energy for your workout while consuming them after exercise can help replenish energy stores in your muscles and thus aid recovery.
If you are a bodybuilder in a bulking phase and have low energy right before a workout, maybe because you have not eaten for a while, you would benefit from fast-digesting carbs before working out.
If you are a runner or cyclist doing strenuous exercise for more than 60 minutes, you would benefit from a mix of fast-digesting carbs while working out, to help support performance by increasing your energy stores.
My Recommendation As A Dietitian
It’s also important to consider that the number of carbs needed to fuel performance can change based on the duration and intensity of the exercise.
“Carbohydrate intake advice is independent of body weight as well as training status. Therefore, although these guidelines apply to most athletes, they are highly dependent on the type and duration of activity ”– Journal of Sports Medicine
This means that carb advice differs based on many factors.
As such, my advice for a bodybuilder or strength athlete low on energy before a workout would be to aim for a smaller quantity, such as 15-30g of fast-digesting carbs.
After a workout, they could replenish energy stores with 30-60g of fast-digesting carbs.
For a runner or any other endurance athlete, this would be a larger amount, such as 30-60g after an hour of exercise (and for every hour after the first 60 minutes).
Here are some examples providing around 30g of fast-digesting carbs:
- 500ml isotonic drink 6g carb/100ml
- One (50 g) energy gel
- Pure dextrose powder (approximately 25g scoop) with 100ml water
- 1 large ripe banana (150g)
When Should You Avoid Fast Digesting Carbs?
You should avoid excessive consumption of fast-digesting carbs if you have issues controlling your blood sugars. Consuming these foods long-term can contribute to the development of insulin resistance (increasing the risk of developing diabetes).
Insulin resistance is a condition where the body becomes less responsive to insulin and therefore unable to regulate blood sugar levels effectively.
You should also limit fast-digesting carbs if you are trying to lose weight because fast-digesting carbs generally contain more simple carbohydrates and less fiber, meaning that blood sugars spike and drop quickly, causing you to feel hungry too quickly after eating.
If you are trying to lose weight, the bulk of your carbs should come from complex carbs with fiber (slow-digesting carbs), which will help you keep your blood sugar levels stable and feel fuller for longer.
If you also pair slow-digesting carbs with protein and fat, you will further slow the digestion and absorption of energy from the meal, which will support hunger levels and blood sugar levels.
This can cause you to consume fewer calories overall because you’re satisfied for longer, making it easier to lose weight.
However, fast-digesting carbs can be included in moderation while cutting especially if you’re noticing you lack energy before working out. If this is something you’re struggling with, check out my other article: Can You Take Dextrose While Cutting?
Learn More About Carbs
If you want to learn more about specific carbs and how fast they digest, check out my other guides:
- Is Bread a Fast or Slow Digesting Carb?
- Is Yogurt Fast Digesting?
- Is Oatmeal a Fast or Slow Digesting Carb?
- Is Banana A Fast or Slow Digesting Carb?
- Is An Apple A Fast Digesting Carb?
- Is Sweet Potato Fast Digesting?
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About The Author
Giulia Rossetto is a qualified Dietitian and Nutritionist. She holds a Masters in Human Nutrition (University of Sheffield, UK) and more recently graduated as a Dietitian (University of Malta). Giulia aims to translate evidence-based science to the public through teaching and writing content. She has worked 4+ years in clinical settings and has also published articles in academic journals. She is into running, swimming and weight lifting, and enjoys spending time in the mountains (she has a soft spot for hiking and skiing in the Italian Dolomites).
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