Carbs and Bodybuilding – Before, During and After Workouts

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By David Thoreau

Updated on

fact checked

Carbs get a bad rap – but they are essential if you are into bodybuilding, working out or training. Some famous diet plans go so far as telling us we should eliminate carbs completely. Some athletes even report they have gone “carb-free” (though quite what what they think fruit and most vegetables are comprised of, if not of carbohydrates, is a mystery).

The problem with this mentality is that carbs are not only important but they are essential in abundance if you are to succeed in your bodybuilding or workout goals.

When it comes to training, we cannot afford to leave out this vital macro-nutrient; it’s the only thing stopping you from grinding to a halt 20 minutes into a workout.

“Hitting the Wall” – aka Crashing

Have you heard the phrase “hitting the wall”? Chances are you have, and I would even wager that, at some point or another, you have hit said wall.

This happens when we don’t provide our muscles with ATP (adenosine triphosphate, the muscles’ main energy source) because we haven’t consumed enough glucose (the main fuel to create ATP). And any high-intensity activity we were engaged in suddenly becomes an exercise in sitting down and feeling weak. Wall = Hit.

What can we do?

Easy. Supply our bodies with enough fuel in the form of carbohydrates to maintain the exercise and then keep supplying it for hours after.

Yes the amounts should be monitored so as to avoid hypo or hyperglycaemia but there are rules of thumb for these things and it’s fairly simple.

Well, OK, to be honest, there will be times when you will get the balance wrong (and it won’t be serious at all – bit of a stomach upset at most) but it’s all about finding what works for you and I’d defy the pros to get it right every time. Anyway, on to the science bit, I’ll try to be brief.

carbs and working out

What Are Carbohydrates?

Carbohydrates are built from simple sugar molecules called monosaccharides, the most abundant of which is glucose, galactose and fructose.

When two or more monosaccharides link together to make a chain, they become disaccharides (2 monos), trisaccharides (3) and so on (we can call them polysaccharides when they get too long to bother counting them).

Generally, carbs are lumped into two groups: complex and simple. This designation depends on the length of their chain.

More importantly, the chains need to be broken down to the individual monosaccharides before they can be absorbed into the blood stream and used as energy. So, as you have probably guessed, the more complex the carbohydrate is, the slower it can be utilized by the body.


What is Glycogen?

Glucose can be used almost immediately to fuel metabolic processes. However, it can also be stored in the form of glycogen for later.

Glycogen is in turn stored in the liver and muscles and becomes the body’s main store of energy for use during exercise. The size of this glycogen reserve depends on a person’s diet, training regime, size, insulin sensitivity (we’ll get to that) and so on.

Blood sugar is what keeps our brains fuelled and stops us experiencing mental fatigue. Mental fatigue equates to muscle fatigue no matter how much glycogen we have stored in our muscles. When blood glucose drops, our bodies replace it from the liver and when that is depleted we can get into trouble.

This is why taking on carbs as we exercise can be vital. Even if our muscles are full of glycogen, that is being used for aerobic or anaerobic glycolysis to make our muscles work. If our brain isn’t fed then it is all worthless.

On average, we can store about 350 grams of glycogen in our muscles and another 90 grams in our liver. This can be increased pretty dramatically in athletes.

The store of glycogen is good for up to 3 hours of medium intensity exercise but high intensity exercise could burn though it in just 30 minutes. And after it’s gone, the body has to source energy from elsewhere and it won’t be as efficient at all. One of those other sources is protein.

Now, really, we want protein to be left alone to create an anabolic (growth) environment in our muscles and while certain supplements like Branched Chain Amino Acids (BCAAs) are a good source of intra-muscular fuel during exercise, it is better to keep our carbohydrate reserves topped up.

Fat is another excellent energy source but when we are deep into an intensely anaerobic workout, its the carbs that our bodies will access the quickest.

It is worth mentioning here that fat is still burned during highly intense exercise but at a lower proportion than low-intensity.

People often think losing fat is synonymous with low-intensity exercise but the truth is that high-intensity may burn less fat in proportion but it will burn more in total over an equal time period. So, if fat loss is your goal, you should still go hard at it for that hour long routine.

Glycemic Index for carbs

Glycemic Index

Developed so that diabetics could monitor their blood sugar levels as well as possible, the glycemic index is a system of categorizing foods. Rate of digestion is the biggest factor determining a food’s impact on blood sugar level.

The slower the digestion rate, the less “glycemic” it is. Therefore, the glycemic index attributes a numbered rating to the food depending on its blood sugar elevating effect.

The index was originally designed to go from 0 (no blood sugar response) to 100 (maximum increase) but some really speedy digesting carbs are listed above 100.

55 and below = low GI (glycemic index)

examples: apples; long-grain rice; canned baked beans

56-69 = moderate

examples: sweet potatoes; brown rice; couscous

70+ = high

examples: honey; cornflakes; dates

Lower GI foods trigger a lower or less dramatic spike in insulin levels (the hormone responsible for nutrient partitioning) which can mean less fat is retained to use as storage.

The average person, therefore, tends to be able to manage their carbohydrate and fat stores better with moderate to low GI diets.

That’s not to say that simple (fast) sugars don’t have their place, but elevated blood sugar can lead to detrimental health conditions (including type 2 diabetes) if they are consumed chronically and in excess.

That said, high GI foods can be used to an athletes advantage and for the high intensity workouts, they have an important role.

If you are interested in the different ways to supplement with carbohydrates before, during and after exercise, please look out for other posts.

Carbs BEFORE Exercise

Supplementing with carbohydrates before exercise will have its greatest effect and is really only needed if muscle glycogen stores are low as you begin exercising.

Pre-exercise supplementation may not even be necessary if the workout is to last less than around 30 minutes. Similarly, if you have eaten carb rich food leading up to exercise, you may not need to supplement at this point.

Remember: supplementing is to add to our diet when that alone is insufficient. Try not to start replacing food with supplements.

A half-hour to an hour before training, consume around 45 grams of carbohydrates (more like 30 grams for someone weighing 160 lbs and more like 60 grams for someone weighing 230 lbs).

It appears that high, moderate or low glycemic index sugars are fine as long as the levels remain stable.

Once you have started on high GI carbs you have to keep consuming them to avoid the infamous “crash” during your workout. Therefore, it is our opinion that moderate GI carbs are more suitable for this initial pre-workout phase.

Carbs DURING Exercise

Depending on the length of your workout, you may need to supplement as you go. A high intensity session, or one lasting over an hour may not be fuelled sufficiently by the pre-workout carbs you took.

Furthermore, if you opted to go without a pre-workout supplement then it might be more important to get some in as you go. Eating food is not impossible during exercise but a carbohydrate drink is much more accessible, not to mention less messy!

This is where high-GI carbs are useful for fast replenishment of your glycogen stores.

A drink containing maltodextrin should do fine here. Again somewhere either side of 45 grams per hour of exercise will work. Too much and you could get an upset stomach.

A little protein or branched chain amino acid powder in the same drink mix will go a long way to reducing your exercise induced catabolism as well. We say 5 grams of BCAAs or 10-15 grams whey protein isolate should do the trick.

Carbs AFTER Exercise

The post-workout window is critical for replenishing nutrients. If ever there were serious gains to be made from training, it’s in the recovery period.

During the first 30 minutes to an hour after a workout our bodies are primed for the replenishment of glycogen stores and it is absolutely key to get it right during this period of time to be able to bounce back fully the next day.

If this window is missed, it will take much longer to recover completely enough to exercise at full potential again.

After exercise, the muscles are also ready to synthesize protein and the mechanisms for amino acid transport and nutrient partitioning (insulin sensitivity) are intensified.

A combination of protein and carbohydrates will work synergistically to improve muscle repair, decrease catabolism (muscle breakdown) and replenish glycogen stores.

Obviously, specific needs will depend on the person but the below indicators might help when you have your scoops ready to fill your shaker cup. This is for within the 2 hours immediately after exercise.

Exercise Intensity | Low to med | Med to high | High | BodybuildingProtein (g)                      5-20            20-30        30-40        40-50Carbs (g)                       30-40          40-60         60-80       80-100

NOTE: The above quantities of protein and carbohydrate supplements would ideally be consumed as soon after training as possible.

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about the author

David Thoreau is a Biotechnologist with a background in life sciences. He has worked for many years on research projects that have helped people improve their quality of life. David has enjoyed collaborating with other scientists around the world, and he loves sharing his knowledge to help educate others about biotechnology.