I’m no fan of fasted training and fasted training is all the rage these days.
Have you ever heard how fasted trainers or low carbers often say that when they had some carbs, their workout was awesome, but that they can’t continue to have carbs because carbs are bad…?
Carbs aren’t bad and fasted training isn’t healthy. I’ll link references to my claims at the bottom of this article.
This article is for those that know that carbs help to fuel their workout and improve their exercise performance and want to know what kind of carb will give the best results.
Or perhaps you’re someone that train very early and it’s difficult to have something right before training that will not cause stomach upset, low blood sugar, nausau, etc.
I’ll be covering all of it in this article.
Why having carbs before your workout is a good idea
If you’re someone that exercises later in the day, then this will apply to you. This study found that those who ate carbs for breakfast had better exercise performance in the evening vs those who didn’t eat carbs for breakfast, even though they compensated for it at lunch (so pre-workout calorie and carb intake were the same in both groups) (R).
Carbs are the preferred fuel source for high-intensity exercise and research even shows that boosting fat oxidation before and during endurance exercise (with low GI carbs) doesn’t boost exercise performance (R).
So eating carbs that reduce fatty acid oxidation during exercise will not impair endurance exercise. And according to many anecdotal reports, exercise feels better and less of a chore when carbs are consumed beforehand.
In a fasted state, liver glycogen is low and cortisol and muscle protein breakdown is elevated. Adding some form of exercise will synergistically enhance cortisol and muscle protein breakdown. In the long run, fasted training will become detrimental.
Having carbs before exercise enhances mood and cognition, which also translates to better eye-hand/foot coordination, better agility, focus, skill performance, fine motor speed, psychomotor speed, and visual discrimination speed, etc (R).
A high carb availability has also been positively related to the exercise-induced adaptations to resistance training (R).
Which kind of carbs are best
The goal with pre-workout nutrition is to:
- Top up glycogen stores.
- Supply the muscles with glucose in order to spare glycogen stores. As a side note, glucose oxidation generates less reactive oxygen species than fat oxidation, so it has a lesser chance of disrupting cellular function.
- Minimize gastric upset and related symptoms and maximize intestinal absorption of the carbs to provide rapid energy availability.
Let’s address the first one.
#1 Top-up glycogen stores
Liver glycogen can be substantially reduced after an overnight fast and is almost completely reduced after 24-36 hours of fasting. However, it will never go to zero and stay there, because the body can produce its own glucose (gluconeogenesis) and store that after long term adaption.
Carbs are the best, fastest and safest way of replenishing glycogen stores. Most people think glucose and insulin are all that’s needed, but the coingestion of glucose with either galactose or fructose can double liver glycogen repletion rates (R).
Muscle glycogen is relatively stable if you’re inactive, so there’s no need to replenish muscle glycogen first thing in the morning, unless you haven’t already done so post-workout from your previous session. But if you want to replenish muscle glycogen right before your next session…you’re doing it wrong (unless you have a second session on the same day). Regardless, if for some reason you have not replenished muscle glycogen the day before, or are doing another workout later in the day, pre-workout carbs have been reported to increase glycogen stores by about 42% (R).
If you use glucose on its own, then 0.8-1.2g/min is the way to go for glycogen resynthesis, but if you combine the glucose with fructose, you can boost that to >1.5-1.7g/min.
Some people think that you need starches to maximally replenish muscle glycogen. However, this study found that fructose is equally effective as glucose at replenishing muscle glycogen and that combining glucose with sucrose or fructose slightly enhances glycogen replenishment (R, R).
Finally, there is evidence that sugarcane juice (a natural drink popular in most tropical Asian regions) are superior for hydration post-workout compared to plain water or sports drink during exercise in a comfortable environment (<30°C) because it’s so effective at enhancing muscle glycogen resynthesis (R).
#2 Supply the muscles with glucose to spare glycogen stores
This is where the following question comes in – should I have low or high GI carbs before training?
The problem with high GI, such as white rice, white potatoes, white bread, etc., is that it spikes blood sugar and insulin and that often causes hypoglycemia during the workout. However, the benefit of high GI, is that you can down a high amount of carbs, whereas with low/medium GI, you have to eat a whole lot more to get the same amount of carbs. This usually puts strain on the digestive system, which causes digestive upset.
The reason we want high-ish GI and high carb intake pre-workout is because it’s better at keeping serotonin low and enhancing performance and glucose oxidation (R). Serotonin potently inhibits exercise performance, and that’s why lowering it has ergogenic benefits. Carbon dioxide is a potent serotonin antagonist and you can learn more how to lower exercise-induced serotonin and increase carbon dioxide production here.
So ideally, we want something that doesn’t spike blood sugar and cause hypoglycemia but provides a lot of carbs per serving.
The absolute ideal carb for that IMO is a carb source that’s a blend between glucose and fructose. So that would be fruit juice, honey, maple syrup, etc.
I’ve found that milk digests too slow, so I might experience some gastric upset if I try to consume 50g of carbs through milk and honey 30 minutes before a workout. If it’s 60 minutes before a workout, then that works better.
Fruit juice on the other hand digests very fast and gives me smooth energy throughout my workout. It’s easy for me to drink 500ml of apple juice and then go train 15 minutes later.
The co-ingestion of glucose and fructose also enhances glucose oxidation more so than either one alone, and this can also boost high-intensity exercise performance.
For example, according to this study, sprint power was higher with 0.8 ratio of fructose to glucose, over a 0.5 ratio (R). Meaning, 20g glucose with 16g fructose mix was superior to 20g glucose with 10g fructose.
This study showed that the ratio of glucose and fructose between 0.8 to 1:1 at rates of >1.7g/min is superior for glucose oxidation and exercise performance (R). Fruit juice, dried fruit or fruit concentrate is ideal for this since most fruit have about a 50:50 ratio glucose to fructose. Honey and maple syrup are also great options to add to milk to increase the carb content.
To simply things, around 50g carbs 30 minutes before training of a 50:50 glucose fructose mix is ideal for replenishing glycogen stores, optimizing glucose oxidation and preventing hypoglycemia, which will translate to better exercise performance, more volume in the gym and ultimately better gains.
#3 Minimize gastric upset and maximize absorption speed
Lots of athletes consume lots of carbs right before and during their training, so it’s absolutely necessary to consume a carb source that’s very easily and quickly absorbed to prevent digestive upset.
However, I should mention that there is a point where faster gastric emptying doesn’t further enhance exercise performance. Hydrogels, which enhances gastric emptying, doesn’t translate to better exercise performance or reduced gastric upset during exercise, compared to other quick absorbed carbohydrates (R).
Combining glucose with fructose
Combining glucose, maltodextrin, dextrose or some kind of starch with fructose, enhances gastric clearance.
According to this study combining O.5g/min fructose with 0.6g/min maltodextrin enhanced gastric emptying and prevented nausea (R).
That’s why I’m a big fan of having fruit juice before my training. It’s easy to chug fruit juice before hitting the gym (or even intra-workout). However, if you’re an endurance athlete, you don’t want to be carrying lots of liquid with you. In that case, 100% fruit juice concentrate is a good option or some of the modified starches.
Amylopectin:amylose ratio of starches
When it comes to regular starches (non-modified), a higher amylopectin:amylose ratio speeds up digestion and gastric clearance. Waxy and glutinous barley, potato and rice are high in amylopectin. However, because amylopectin digests so rapidly and is commonly more insulinogenic than amylose, it might cause hypoglycemia during the workout.
High molecular weight vs low molecular weight starches
Furthermore, when shopping for modified starches, look for something that is high molecular weight (HMW), and low osmolality, such as Vitargo®.
HMW starches digest and absorb quickly and don’t cause a spike in insulin and subsequent hypoglycemia. High-molecular weight starch-based carbohydrates have been shown to replenish muscle glycogen more rapidly (167% faster) when compared to lower molecular weight (R).
Also, a carbohydrate of lower osmolality will empty faster than one of higher osmolality, especially at high concentrations (R). This is important for endurance athletes because they have to consume condensed sources of carbs.
According to this study, Vitargo® (a HMW, low osmolarity starch-based carbohydrate) led to a greater work-output during a 15-minute time-trial 2 hours following cycling to exhaustion when compared to maltodextrin (a low molecular weight (LMW) carbohydrate) (R).
This difference in starches doesn’t just matter for endurance training, but also weight training. This study found that a high molecular weight starch vs LMW enhances weight training performance during the squat (R).
Highly branched cyclic dextrin (HBCD) is also a high molecular weight and low osmolarity carbohydrate.
It boosts exercise performance better than equal amounts of maltodextrin or glucose.
This study compared glucose vs HBCD and found that post-race urinary cytokines, namely IL-8, IL-10 and IL-12p40 concentrations were significantly lower in the HBCD trial compared with the glucose trial (R). Also, HBCD lowered noradrenaline levels to a much greater extent than glucose, which shows that it’s superior to glucose at boosting glucose oxidation, lessening the need for free fatty acids.
HBCD absorbs very quickly and causes very little to none gastric issues.
This aspect of HBCD makes it a great intra-workout supplement as well.
In terms of intra-workout food/carbs, there is a concern that the food/carbs will not absorb, because of the fact that exercise inhibits proper digestion and absorption. This is because the noradrenaline released during exercise shuttles blood flow away from the digestive organs and towards the muscles. However, this study found that during moderate exercise (less than 75% VO2max), gastric emptying occurs at a rate similar to that during rest; whereas more intense exercise appears to inhibit gastric emptying (R).
So having something that digests and absorbs very fast is still good to have intra-workout (during low to moderate intensity endurance training or weight training) as your body will still absorb it as usual and use it without any delay.
Two other carb sources I’d like to talk about
Ribose is a sugar that’s created endogenously through the pentose phosphate pathway. Ribose helps with recycling ATP through the salvage pathway in which the mitochondria uses ATP metabolites (e.g. AMP, ADP) to form new ATP molecules. The traditional way of creating ATP through oxidative phosphorylation is slow and the salvage pathway is much faster.
Ribose is frequently used for patients with heart failure or other heart complications. What few people know is that your heart is one the major regulators of exercise intensity. The better your heart can produce energy, then more intense you can exercise. If your heart can’t produce enough energy, you won’t be able to train very hard.
In terms of exercise performance, this study found that 10g d-ribose daily was better than 10g dextrose at maintaining exercise performance, as well as reducing levels of RPE (rate of perceived exertion) and CK (creatine kinase) in people with lower VO2 max, but not with higher VO2 max (R).
There is also evidence that ribose could potentially work great with caffeine and help to prevent the crash afterwards (R).
Ribose might not be very effective for highly fit with healthy hearts, but might be useful for those that aren’t so fit and need a good sugar for their heart.
Honey is also a great pre-workout carb. Here are a few reasons why.
- Aids in the rapid replenishment of glycogen stores.
- Helps to keep blood sugar stable. Prolonged and/or intense exercise can lead to immunity impairment and an increased risk of sustaining upper respiratory tract infections.
- Is effective at suppressing inflammation long term. Exercising in a carbohydrate-depleted state (i.e., following days of low carbohydrate intake and/or prior glycogen depleting exercise) disrupts several markers of immune function (e.g., IL-6, IL-1ra, IL-10, TNF-α).
- Helps to keep stress hormones low (low carbohydrate intake and/or prior glycogen depleting exercise elicits greater elevations in circulating stress hormones) (R).
- Is rapidly absorbed and doesn’t cause GI upset.
- Doesn’t spike insulin nearly as much as starches, so doesn’t cause the hypoglycemia issue (R).
- Enhances bone formation (R). Bone loss is common in long distance runners, especially if they’re low carb as well.
So how much should you take pre-workout?
It depends on if you’re fasted or not, what you had for the previous meal, how long before the workout you had you previous meal, how active you were before your workout, what kind of workout your going to do, etc.
Weight training performance
When it comes to weight lifting performance, then 30-50g pre-workout is a good amount. That would be about 1/2 to 1L of milk. However, milk specifically might take a while to digest, but you should be good to go if you have it 60 minutes before your workout.
If you want to reduce the liquid, but up the carbs, then you can add 1-2 tbsp honey or maple syrup and also benefit from the fructose content.
500ml of fruit juice has around 50-60g of carbs and is very easily digested and absorbed, so you have it 30 minutes pre-workout. This is what I do and it works great.
Endurance exercise performance and recovery
But if we were to speak about recovery from long-distance running, then even higher amounts are necessary.
When comparing 60, 90 and 120 g/h of carbohydrate intake during a mountain marathon, 120g/h is superior to the rest in limiting neuromuscular fatigue and improving recovery (R).
Whilst it was traditionally believed that ~60g/h represented the upper limit of carbohydrate (i.e., glucose) oxidation during endurance exercise, more recent evidence suggests that simultaneously ingesting carbohydrates from multiple sources (e.g., glucose and fructose) may increase oxidation capacity by up to ~75%. Notably, consuming a combination of glucose and fructose at a rate of 108–144g/h improves performance during prolonged cycling exercise when compared with the equivalent dose of glucose alone (R).
For weight training, take 30-50g carb (preferably a 50:50 glucose fructose mix) 30-60 min pre-workout. Combine with 20-30g protein or 10-15g EAAs.
Pre-workout examples would be:
- 500ml of apple juice with 15g EAAs 30 min pre-workout (15g protein + 60g carbs)
- 500ml low fat/skim milk with 10g EAAs, 2 tbsp maple syrup/honey (27g protein + 50g carbs)
- 250-500ml water with 15g EAAs, 45g Vitargo and 5g ribose (15 protein + 50g carbs)
- Fasted training is not superior for fat loss
- Higher fat oxidation doesn’t translate to better fat loss
- Excess carb intake doesn’t translate to excess fat synthesis and fat gain
- The dark side of carnitine
- How to optimize glucose oxidation
- The dope on blocking fatty acid oxidation
- How to improve insulin sensitivity without going low carb
As always, thanks so much for reading my article. Let me know in the comments below if you have any questions. And if you found this article to be insightful and helpful please like and share so this information can help others as well.
Have you signed up for my Fun Fact Friday Newsletter yet?
If not, you don’t want to miss out.
Every Friday I share a weekly special, with my readers, of the small things I did and learned that week; things I found interesting, maybe a good book I read, something I’m experimenting with, an exercise that’s giving me great results, a new supplement I’m trying out, an inspirational quote, things like that. I also give a link to the article I did that week so you can stay up to date with my articles.
Want to join us?