Carb timing refers to how you schedule your carbohydrate intake around your workouts, and it’s a topic that spurs furor in the fitness space.
Some people believe eating carbs immediately before and after you train is of prime importance because it’s the only way to maximize your performance and recovery.
Others disagree. They say eating pre-workout carbs allows you to train longer and harder, which boosts muscle and strength gain over time, but post-workout carbs do little to facilitate progress.
Still others have the opposite opinion, claiming pre-workout carbs are of little account, but post-workout carbs replenish your energy and prep your muscles for future workouts.
Sussing the facts from the fallacies can be challenging, too, because every argument seems plausible at face value.
In this article, we’ll call on science to help answer this simple question.
When is the best time to eat carbs?
What Is “Carb Timing?”
For decades, scientists, athletes, and bodybuilders have tried to pinpoint the perfect time to consume each macronutrient to maximize performance and results. This is called nutrient timing.
Carb timing is one part of nutrient timing that involves finding the best time to consume carbohydrates to fuel your workouts, boost muscle growth, and accelerate recovery.
Most often, people “time” their carb intake around their workout schedule. For instance, they might eat a high-carb meal in the few hours before and after they train.
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Why Is Carb Timing Important for Weightlifters?
Your body breaks down most of the carbs you eat into glucose, the main energy source for the brain, central nervous system, and cells.
When you feed your body more glucose than it needs, it stores the surplus in your liver and muscles. This stored form of glucose is called glycogen, and it’s the primary fuel reserve for your muscles during intense exercise.
Many weightlifters believe that consuming carbs at specific times helps to keep your muscles brimming with glycogen, which allows you to train longer and harder and recover faster, leading to more muscle and strength gain over time.
Does Carb Timing Matter?
Let’s take a look at what the science says about how pre- and post-workout carbs affect your weightlifting performance and recovery.
A common refrain within weightlifter circles is that you should consume carbs before you train to top off your glycogen stores and give yourself the energy you need to perform well in your workout.
And while this seems like a reasonable slant, research on the performance impact of pre-workout carbs is surprisingly mixed.
For example, scientists at The International Scientific Research Foundation for Fitness and Nutrition recently performed a meta-analysis investigating how carbohydrate intake affects weightlifting performance.
As part of the study, the scientists dug into the research on pre-workout carbs to see which way the weight of the evidence sways.
They found that in 11 out of 19 studies, consuming pre-workout carbs had no effect on performance. Of the 8 studies that showed carbs had an effect, 2 found that consuming a small amount of pre-exercise carbs was more beneficial than consuming a large amount, while 6 favored higher carb intakes.
This is unusual since, if carbs improve performance, you’d expect higher doses to have even more benefits, but that’s not what happened.
Furthermore, in the six studies that showed loading up with carbs was advantageous, the participants who consumed more carbs also consumed more total calories. This makes it impossible to know whether the extra energy or timing of the carbs caused the performance improvement in these studies.
The only other time pre-workout carbs appeared to be a boon for performance was in studies when the participants were hungry.
Even then, there didn’t seem to be anything special about ingesting carbs. The participants experienced a similar performance boost whether they filled their stomachs with a carb-rich gel or an identical low-carb alternative. In other words, it wasn’t the carbs that made the participants perform better, it was the feeling of fullness and lack of hunger.
Thus, consuming a ton of pre-workout carbs probably isn’t necessary. Ensuring you’re not peckish might, but you could do that by eating any macronutrient. In fact, fueling up on protein is likely a better solution since some research suggests pre-workout protein has a small but positive effect on muscle gain over time (and would help dampen hunger, too).
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The main argument for consuming carbs after your workouts is to replenish your diminished glycogen stores so as not to hamper your recovery and performance in future workouts.
Despite this stance seeming sensible enough, research doesn’t agree. And that’s because weightlifting workouts simply don’t deplete glycogen levels enough to necessitate rapid replenishment.
For example, in a study published in the European Journal of Applied Physiology, weightlifters who did 5 sets each of the front squat, back squat, leg press, and leg extension, all to failure, only diminished glycogen levels by ~26%.
In another study conducted by scientists at the Swedish University of Agricultural Sciences, bodybuilders who alternated between 30-second bouts of heavy leg extensions and 1-minute rest intervals for 30 minutes only drained their glycogen stores by ~28%.
Other studies show that relatively high-volume workouts (9-to-12 sets) for a single body part might deplete glycogen levels in the trained muscle by up to ~40%, but that’s still not enough to warrant concern, especially since weightlifters in the real world likely wouldn’t train that muscle again for at least a few days.
In the interim, eating even a moderate amount of carbs would be enough to replenish everything that was lost. Moreover, the body closely regulates glycogen levels, so the more you lose, the more quickly it’s replaced.
At bottom, weightlifting doesn’t deplete glycogen stores like endurance exercise, such as cycling, running, or soccer. As such, topping up your glycogen stores with post-workout carbs isn’t of paramount importance.
Another reason people believe consuming post-workout carbs is crucial concerns insulin.
Insulin plays a vital role in the muscle-building process because it shuttles amino acids to your muscles, increases muscle protein synthesis rates, and decreases muscle protein breakdown rates, and many people believe that the best way to amplify its benefits is by eating insulin-boosting post-workout carbs.
However, studies show that consuming post-workout carbs is no more effective at maximizing insulin’s anabolic effects than consuming post-workout protein, and since protein stimulates muscle building and carbs don’t, it’s probably sensible to prioritize protein and only consume carbs if you want to.
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Many people get mired in the minutia of carb timing, but they needn’t. Studies show that when you eat carbs has little impact on how productive your training is or how well you recover.
What’s more important is that you eat the right amount of each macronutrient and number of calories to support your long-term body composition and performance goals.
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