Carbohydrates for Performance: How Much Do You Need and When?
Carbohydrates have had an interesting few decades. For athletes, they have traditionally been viewed as essential fuel. In the wider fitness world, however, carbohydrates have alternately been blamed for fat gain, insulin resistance, poor health and just about every stalled diet imaginable. More recently, performance nutrition has moved in almost the opposite direction, with some endurance athletes consuming remarkably large amounts of carbohydrate during competition.
So where does that leave the recreational athlete, HYROX participant or active adult who simply wants to train and perform well? The answer is neither “eat as many carbohydrates as possible” nor “avoid them unless absolutely necessary.”
A better approach is to understand what carbohydrates actually do and then match carbohydrate availability to the demands of your training. That is the central idea of this article. You do not need the same amount of carbohydrate every day. You do not need to eat carbohydrates constantly to preserve muscle. And a 45-minute strength session does not create the same nutritional demands as a hard HYROX simulation, long run or two-a-day training schedule. Your nutrition should reflect that.
What Happens When You Eat Carbohydrates?
Dietary carbohydrates are broken down primarily into glucose, which can be used immediately for energy or stored for later use. A significant portion is stored as glycogen, predominantly in skeletal muscle and the liver. Muscle glycogen provides a readily available source of carbohydrate during exercise. Liver glycogen helps maintain blood glucose, particularly between meals and during prolonged activity.
Your body can also generate glucose through other metabolic pathways, so carbohydrates are not technically an essential nutrient in the same sense as certain amino acids or fatty acids. That observation sometimes leads to the argument that athletes therefore do not need carbohydrates. Physiologically, that misses the point.
The relevant question for an athlete is not simply:
“Can the body survive without dietary carbohydrate?”
It is:
“What fuel availability best supports the training and performance I am asking my body to produce?”
Those are very different questions.
Why Exercise Intensity Changes the Equation
Your body can generate energy from both fat and carbohydrate. At lower exercise intensities, fat can contribute substantially to energy production. As intensity rises, however, carbohydrate becomes increasingly important because it can support rapid rates of energy production.\
That matters when you sprint, run hard, perform repeated intervals, push a sled, complete high-repetition functional movements or sustain demanding race pace.
In other words, many of the activities we associate with athletic performance are precisely the activities where carbohydrate availability becomes useful.
This is one reason carbohydrate intake is so well established in endurance sport. Research consistently shows that consuming carbohydrate during prolonged endurance exercise can improve performance, with the benefits generally becoming more meaningful as exercise duration increases. The practical lesson is straightforward:
The harder and longer you intend to work, the more attention carbohydrate deserves.
Carbohydrate Needs Should Follow Training Demand
One of the weaknesses of generic nutrition advice is the tendency to prescribe a single carbohydrate target and apply it every day. Athletes do not train the same way every day.
Nutrition does not necessarily need to remain identical either. A recovery day has different energy requirements from a two-hour endurance session. A short upper-body workout has different glycogen demands from a high-volume lower-body session.
A technical training session is different from a HYROX simulation.
This is where the idea of cycling carbohydrate intake becomes useful. On lighter training days, carbohydrate intake can be lower because the requirement for rapid energy production and glycogen replacement is lower. On demanding training days, increasing carbohydrate availability can help support training quality and recovery.
Around competition, carbohydrate intake may increase further. This does not require complicated nutritional mathematics .It simply means allowing your food intake to reflect what you are asking your body to do.
How Much Carbohydrate Do You Actually Need?
Sports-nutrition guidelines commonly express carbohydrate intake relative to body mass because training demands can vary enormously between athletes.Depending on training volume, recommendations across athletic populations can range from approximately 3–5 grams per kilogram of body weight per day for relatively light training to considerably higher intakes during demanding endurance programmes.
Elite endurance athletes undertaking very large training volumes may require 8–12 g/kg per day in certain situations.
That does not mean everyone who exercises should start eating 8 g/kg of carbohydrate.
For an 85-kilogram athlete, that would represent 680 grams of carbohydrate per day.
That could be entirely appropriate in a high-volume endurance context and completely unnecessary for someone strength training four times per week.
Rather than chasing the largest number in a guideline, start by asking:
How much training am I doing?
How glycogen-demanding is that training?
Am I training once or multiple times today?
Do I need to perform again tomorrow?
Am I trying to maintain weight, gain muscle or lose fat?
And most importantly: Is my current carbohydrate intake supporting my training?
Guidelines provide a range. Performance tells us where within that range you probably need to be.
Carbohydrates and Strength Training
Carbohydrates are often discussed as though resistance training cannot be performed effectively without a large carbohydrate intake. The evidence is more nuanced. For someone who has eaten normally before training and completes a conventional resistance-training session, consuming additional carbohydrate immediately before or during the workout does not consistently improve performance. That makes sense.
A normal strength session is not equivalent to running a marathon. However, carbohydrate becomes more relevant as resistance-training volume increases, sessions become longer, muscle glycogen is already depleted or multiple demanding sessions occur within a relatively short period. This distinction matters.
If you train for 45–60 minutes after eating several normal meals, you probably do not need a sports drink simply because you are lifting weights.
If you are performing a long bodybuilding session with substantial volume, combining lifting with conditioning, or training twice in one day, carbohydrate availability becomes increasingly relevant.
Nutrition should follow the demand.
Carbohydrates and HYROX
HYROX provides an excellent example of why carbohydrate recommendations cannot be reduced to “strength” versus “cardio.” A HYROX race combines repeated one-kilometre runs with demanding work stations including sled pushes, sled pulls, burpee broad jumps, rowing, farmers carries, sandbag lunges and wall balls. That creates repeated periods of relatively high-intensity muscular work layered onto sustained aerobic demand.Carbohydrate is therefore highly relevant.
But that does not mean HYROX athletes need to treat every training session like race day.
An easy aerobic session may require little nutritional intervention. A short strength session may require nothing beyond normal meals. A demanding compromised-running session or full race simulation is different. As training demand rises, carbohydrate availability becomes another variable we can deliberately increase. This is the practical value of carbohydrate cycling.
Fuel the work that needs fuel.
Should You Eat Carbohydrates Before Training?
Usually, the closer you get to a demanding training session, the more useful easily digested carbohydrate can become. But pre-training nutrition depends heavily on what you have already eaten. If you train at 5 p.m. after breakfast, lunch and an afternoon snack, you are not entering the gym in the same metabolic state as someone training first thing in the morning after an overnight fast. Context matters.
For a demanding session, a carbohydrate-containing meal roughly two to four hours before training is often a useful starting point.mThe precise amount depends on body size, session duration, gastrointestinal tolerance and the rest of the day's intake. As training approaches, food choices generally become simpler. Foods high in fat, fibre or very large amounts of protein take longer to digest and can create gastrointestinal discomfort during hard exercise.
That is why pre-race foods often look rather less impressive from a “clean eating” perspective than someone's everyday diet. White rice, bread, bananas, cereal, oats, potatoes or similar foods may simply be easier to digest and more useful at that particular time.
Nutrition has a job to do.
Do You Need Carbohydrates During Training?
For many gym sessions: No.
If you are training for less than an hour, have eaten beforehand and are not completing enormous amounts of work, water may be all you need. The situation changes as duration and intensity rise. During sustained high-intensity exercise lasting beyond approximately an hour, consuming carbohydrate can help maintain fuel availability and performance. A commonly used starting range is around 30–60 grams per hour.
For longer endurance events, higher carbohydrate delivery rates can be useful, particularly when combinations of glucose and fructose are used because they can increase total intestinal carbohydrate absorption. Historically, recommendations have extended to around 90 g/h for prolonged endurance activity. More recent research has explored intakes approaching 120 g/h in trained athletes.
That does not mean recreational athletes should immediately aim for 120 g/h. There are two reasons.
First, the benefits of extremely high carbohydrate intakes are most relevant to long-duration endurance competition.
Second, your gastrointestinal system has to tolerate what you consume.
Nutrition during competition should therefore be trained, just like pacing and movement skills. Do not introduce an aggressive fuelling strategy for the first time on race morning.
What About a HYROX Race?
This is where context becomes particularly interesting. A HYROX race for many recreational participants will fall into a duration where carbohydrate intake during the event may be useful. But HYROX also presents practical limitations. You are running. You are repeatedly entering work stations. Your heart rate is elevated. You may already be experiencing gastrointestinal stress.
Trying to consume large volumes of carbohydrate because an endurance guideline says you can is not automatically a good strategy. For many athletes, what they consume before the race may be at least as important as what they manage to take during it.
During-event intake should then be simple, practiced and appropriate to expected race duration. More is not automatically better.
Post-Training Carbohydrates: How Urgent Is the “Window”?
The post-exercise period is another area where useful physiology sometimes becomes an unnecessary rule. Exercise increases the body's ability to restore glycogen. If you have another demanding session within several hours, rapid carbohydrate replacement becomes important. In that situation, aggressive carbohydrate intake immediately after training can help accelerate glycogen restoration.
But if you have finished training at 6 p.m., will eat dinner shortly afterward and are not training again until tomorrow afternoon, there is considerably less urgency. You still need to replace the energy and carbohydrate you used. You simply do not need to panic because you missed a supposed 30-minute anabolic window.
As with most sports nutrition:
The shorter the recovery period, the more timing matters.
Do Carbohydrates Make You Fat?
Carbohydrates do not possess a unique ability to override energy balance. Body-fat gain occurs when energy intake chronically exceeds expenditure and the excess energy is stored. A high-carbohydrate diet can contribute to that surplus. So can a high-fat diet.
So can eating too much “healthy food.”
That does not mean food quality is irrelevant. Nor does it mean different macronutrients have identical metabolic effects. It means blaming carbohydrate itself for fat gain confuses the nutrient with the overall energy environment. This is why the discussion in Energy Balance Explained: How Fat Loss and Muscle Gain Actually Work matters.
If fat loss is the objective, carbohydrate intake has to fit within the overall calorie target.
The question then becomes how much carbohydrate we can retain while still achieving that deficit and supporting training. For an athlete, that is generally a better question than:
“How low can I push carbohydrates?”
Can You Perform on a Low-Carbohydrate Diet?
Humans are remarkably adaptable. With carbohydrate restriction, the body increases reliance on fat oxidation and can produce ketones that provide fuel for certain tissues.
That makes low-carbohydrate and ketogenic diets viable dietary approaches in some contexts.
It does not automatically make them optimal for every performance objective.
The strongest case against chronic carbohydrate restriction is in sports requiring substantial sustained or repeated high-intensity work. Current scientific consensus continues to favour strategies that provide sufficient carbohydrate availability when performance demands it. This is particularly relevant to sports such as HYROX, where athletes repeatedly operate at intensities that make carbohydrate metabolism important.
There may be circumstances where deliberately training with reduced carbohydrate availability is useful. Some endurance programmes use selected “train-low” sessions with the aim of promoting metabolic adaptation. But this needs to be separated from the idea that all training should be performed carbohydrate-depleted. There is a trade-off.
Low carbohydrate availability may alter some cellular signalling associated with endurance adaptation. It can also reduce the quality of high-intensity training.
If the objective of today's workout is to perform hard intervals at race pace, deliberately removing the fuel that supports those intervals may be counterproductive. Adaptation matters. So does the quality of the stimulus creating it.
Food Quality Still Matters
Talking about carbohydrate in grams can make it sound as though all carbohydrate sources are interchangeable. They are not. Most everyday carbohydrate intake should come from foods that also contribute fibre, vitamins, minerals and other useful nutrients.
That can include:
Whole grains.
Rice and potatoes.
Oats.
Fruit.
Vegetables.
Legumes.
Dairy products where tolerated.
The closer you move toward demanding exercise, however, the priorities can change.
High-fibre foods are generally excellent for health. A very high-fibre meal immediately before a hard run may not be excellent for your gastrointestinal system.
Similarly, sports drinks, gels and other concentrated carbohydrate products are not inherently “bad foods.” They are specialised tools. During a race, quickly delivering carbohydrate and fluid is exactly what we want them to do. You do not need to judge a sports gel by the same criteria as breakfast.
Carbohydrates During Fat Loss
One of the first things many people do when dieting is remove carbohydrates. There is nothing inherently wrong with reducing carbohydrate intake when calories need to decrease. Something has to change.
But for athletes, cutting carbohydrate too aggressively can create another problem: the diet begins to interfere with training. A more useful approach is often to establish adequate protein, retain sufficient dietary fat for health and dietary sustainability, and then allow carbohydrate intake to occupy much of the remaining energy budget. As calories become lower, carbohydrate intake may decrease.
But I usually want to protect carbohydrate around the training sessions that matter most.
If you are dieting while preparing for HYROX, for example, being in a calorie deficit does not mean arriving at every hard running session glycogen-depleted.
Fat loss and performance nutrition need to coexist.
Carbohydrates for Muscle Gain
During a muscle-gaining phase, carbohydrates become useful for a different reason.
Resistance training provides the stimulus for hypertrophy. Protein supplies the amino acids required to build and repair tissue. And sufficient total energy supports the process.
Carbohydrate can help support training volume, particularly as programmes become demanding.
But carbohydrate is not itself anabolic magic. Eating more carbohydrate without an appropriate resistance-training stimulus does not create muscle simply because glycogen stores are full. As discussed in the energy-balance article, the objective of a gaining phase is not to consume the largest calorie surplus possible.
It is to provide enough energy to support productive training and gradual tissue gain without unnecessarily increasing body fat. Carbohydrates are extremely useful within that strategy. They are not a substitute for it.
A More Useful Way to Think About Carbohydrates
Rather than categorising yourself as “high carb” or “low carb,” think about carbohydrate in terms of availability and demand. Ask three questions.
What am I doing today?
A recovery day and a race simulation do not require identical fuelling.
How hard do I need to perform?
A technically easy session creates different demands from threshold intervals or high-volume resistance training
How soon do I need to perform again?
Recovery nutrition becomes increasingly important as the time between demanding sessions becomes shorter.
Those questions will usually tell you more than trying to conform to a particular dietary identity.
Match the Fuel to the Work
Carbohydrates are neither essential at every meal nor something athletes should fear.
They are fuel. And like any fuel source, their value depends partly on the work being performed. For someone training moderately a few times each week, ordinary meals may easily provide enough carbohydrate. For an athlete completing high-volume endurance training, repeated intervals or demanding HYROX preparation, carbohydrate becomes considerably more important.
The goal is not to maximise carbohydrate intake. It is to make enough carbohydrate available to support the training and performance you actually care about. That means eating more when the work demands more. Less when it does not.
Paying greater attention to timing when sessions are long, intense or closely spaced.
And judging whether the strategy works by what happens in training—not by whether it conforms to a nutritional ideology.
Fuel the work. Recover from it. Then adjust according to the next demand.
That is a more useful carbohydrate strategy than simply trying to eat “high carb” or “low carb.”
If you want help building a nutrition and training strategy around your performance, body-composition and HYROX goals, apply for coaching with JM Performance Coach.
References
Burke, L. M., & Noakes, T. D. (2026). Does a low-carbohydrate diet impede endurance sports performance? Debate consensus. The American Journal of Clinical Nutrition, 123(5), 101271.
Henselmans, M., Bjørnsen, T., Hedderman, R., & Vårvik, F. T. (2022). The effect of carbohydrate intake on strength and resistance training performance: A systematic review. Nutrients, 14(4), 856.
Kerksick, C. M., Arent, S., Schoenfeld, B. J., et al. (2017). International Society of Sports Nutrition position stand: Nutrient timing. Journal of the International Society of Sports Nutrition, 14, 33.
Ramos-Campo, D. J., Clemente-Suárez, V. J., Cupeiro, R., et al. (2024). The ergogenic effects of acute carbohydrate feeding on endurance performance: A systematic review, meta-analysis and meta-regression. Critical Reviews in Food Science and Nutrition, 64(30), 11196–11205.
Vårvik, F. T., Bjørnsen, T., Gonzalez, A. M., et al. (2022). The ergogenic effects of acute carbohydrate feeding on resistance exercise performance: A systematic review and meta-analysis. Sports Medicine.
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