Workout nutrition advice is everywhere and can leave you wondering what to eat before, during, or after training. That’s why we’re doing a short series on pre-workout, intra-workout, and post-workout nutrition to explore what you might need for your next session and what may be worth testing.
In this first article, we’ll focus on pre-workout nutrition and what the research shows about eating before training. Is it okay to train fasted? Is breakfast enough to support training? Do you need specific amounts of protein or carbohydrate beforehand? We’ll review what the evidence shows to help you make more informed choices.
Let’s dig in.
Why we discuss workout nutrition
To avoid resting on too many assumptions, I’d like to briefly explain why it’s worth examining workout nutrition in the first place.
In simple terms, workout nutrition is about nutrient timing. The core questions are straightforward:
- Can eating before, during, or after training improve performance or recovery?
- How much does timing matter compared with total daily intake?
- And are the effects large enough to make a meaningful difference?
This series takes a closer look at those questions, separating what’s worth paying attention to versus marketing noise. In this first part, we’ll focus on pre-workout nutrition and how eating before training may (or may not) affect performance, fatigue, and your mindset during exercise.
Before we get into specifics, let’s look briefly at what’s happening in your body during training.
A brief look at the body during training
When you start any kind of physical activity, especially structured exercise, your breathing and heart rate increase to meet the demand you’re creating for more oxygen and nutrients in your muscles. Inside those muscles are mitochondria (biology throwback: “powerhouses of the cell”), and all the extra oxygen and blood flow help mitochondria produce adenosine triphosphate (ATP). ATP is the molecule that directly powers muscle contractions. And to keep ATP production going, your body needs a steady supply of oxygen and nutrients.
This is where nutrition comes in, as it ensures you have enough fuel to keep everything running.
In practical terms, workout nutrition is there to ensure you have all the available nutrition necessary to perform during a training session and then recover afterwards. This series asks whether there are real “windows” for workout nutrition or if eating throughout the day is enough.
Scope of this series
This series won’t cover specialized nutrition needs, such as carbohydrate loading for endurance events or macronutrient strategies for bodybuilding competitions. It also won’t focus on specialized diets, such as ketogenic diets. Instead, it focuses on average trainees engaging in resistance or general endurance training while eating a mixed macronutrient diet.
It’s also worth noting that this article doesn’t cover pre-workout products and focuses instead on macronutrient-based strategies. For example, caffeine is a well-established ergogenic aid and is often included in workout products. It’s certainly valid and worth considering before a workout, but it is out of scope for this article. That said, if you’re interested in evidence-based supplement use, we’ve covered them regarding performance, body composition, and health.
Macronutrients in action
Because your body’s ability to use fuel depends on how and which nutrients enter the bloodstream, it’s worth taking a quick look at the role of each macronutrient to understand how each one supports energy production during training.
Carbohydrates
When you eat carbohydrates, your body converts them into glucose, which is an energy source for exercise. They also produce more ATP than fat for the same amount of oxygen. When you train, your muscles mainly use stored glycogen for energy, and as those stores run low, blood glucose helps keep you going.
It’s common to think of glycogen as a single tank of fuel, but it’s more like tons of smaller reserves. Glycogen exists in different compartments, and how it’s accessed depends on training type and intensity.
For example, during a typical resistance training session, total muscle glycogen might drop by about 25 to 40%. However, certain compartments, such as intramyofibrillar glycogen, can run out much faster. Endurance exercise tends to deplete these stores even more quickly.
Glycogen storage varies from person to person, but most people maintain around 400 to 500 mmol per kilogram of dry muscle on a balanced diet. With a higher carbohydrate intake, levels can rise to about 700 mmol, while low-carbohydrate diets can drop them closer to 200 mmol.
Increasing training intensity will obviously increase oxygen use and heart rate, and thus affect glycogen use, increasing its use as exercise intensity increases. At lower intensities, most fuel comes from fat oxidation. This is why people sometimes say that, depending on training intensity, you’re “burning carbs” or “burning fat.”
Energy use at different training intensities
| Energy use at different training intensities | |||
|---|---|---|---|
| Example activity | Intensity (% VO2 max) | Primary fuel source | Glycogen use |
| Walking, light cycling, recovery work | <50% | Mostly fat oxidation | Minimal |
| Steady aerobic or endurance training | 60–70% | Mix of fat and glycogen | Moderate |
| HIIT, sprinting, resistance training | 75–80% | Predominantly glycogen | High |
| Near-anaerobic work | >90% | Almost entirely glycogen | Very high |
| Table inspired by Exercise Physiology (McArdle et al, 2019) and the International Society of Sports Nutrition Position Stand on Nutrient Timing (2017). | |||
The rate of digestion also varies a lot between different carbohydrate sources. Simple carbohydrates break down quickly and provide faster glucose, while fiber-rich foods digest more slowly and can slow stomach emptying if eaten too close to a workout.
| Example of different carbohydrate types | ||
|---|---|---|
| Carbohydrate type | Description and digestive note | Examples |
| Simple | Quickly digestible and made up of shorter sugar chains, they offer a faster surge in energy and are therefore better for more acute energy needs. | Glucose, fructose, sucrose, lactose, honey, fruit juices, and candy. |
| Complex | Made up of longer sugar chains and therefore take longer to break down and deliver more prolonged or steadier energy over a longer period of time. May be harder on the digestive system for endurance training nutrition in the short-term. | Potatoes, brown rice, whole wheat bread, broccoli, oats, and beans. |
| Dietary Fiber | Mostly non-absorbable material that becomes digestive waste. | Soluble fiber – mostly the inner flesh or pulp of plant foods. Insoluble fiber – mostly the outer husks, shells, and tough outer layers of plant foods. |
Fat
Fat oxidation is a slower source of ATP production and contributes more at lower exercise intensities. For example, most energy used at rest and during daily activity comes from fat oxidation.
As training intensity increases, your body shifts more toward glycogen because it can produce ATP from carbohydrates more efficiently and at a faster rate. This changes the ratio of fat to glycogen oxidation, though this ratio varies. For example, in trained individuals, fat oxidation can range from about 0.4 to 1g per minute, with endurance athletes sustaining the higher end of that range even when training harder.
Fat stores are rarely depleted because total body fat provides a much larger energy reserve than glycogen. However, during long or intense sessions, glycogen can be a limiting factor; if glycogen levels drop, fat oxidation will increase, but overall energy output can decline.
From a digestion standpoint, dietary fat moves through your system more slowly than simple carbohydrates. The sustainability aspect of fat as a fuel mainly comes from how much is stored in the body, not from immediate dietary intake.
Protein
Ideally, protein shouldn’t be a main energy source, especially if that protein comes from breaking down muscle. During exercise, your body is designed to draw energy primarily from carbohydrates and fat. That doesn’t mean protein intake isn’t important; it just means that for workout nutrition, the goal isn’t to increase protein oxidation. For protein, you’re ideally looking for recovery or repair, not performance. You want the performance to come from your carbohydrates and fat sources.
If you’re wondering how much protein we can use during training, it varies, but it’s not much. A 2025 meta-analysis by Clauss and Jensen found that protein oxidation made up about 3% of total energy used during endurance exercise, which aligns with other previous estimates. However, this study showed that while energy from protein oxidation is low, it can increase in its ratio with higher exercise intensity or glycogen depletion. This means it’s not just the duration of exercise that matters, but the combination of intensity and carbohydrate availability that could increase protein use.
While it typically takes endurance training to reduce glycogen, training hard in a chronically low-Calorie or low-carbohydrate state could create similar conditions. That doesn’t guarantee muscle loss, but it could increase the likelihood of greater protein oxidation, which most people want to avoid.
Research like this supports the idea of increasing protein intake to cover the small amount you might use during longer workouts. You don’t want to rely on protein as a primary fuel source, but getting enough may help reduce muscle breakdown when energy or glycogen runs low. Lastly, research continues to show that total daily protein intake is the most important factor, as we’ve discussed in many MacroFactor articles.
From a digestion standpoint, whole-food proteins vary in how quickly they are absorbed. In general, liquid proteins like whey digest faster, while whole-food proteins, especially those with more fiber, move more slowly. These differences matter less for performance and more for digestive comfort.
Quick nutrient recap
The main goals of pre-workout nutrition are to fuel your training and reduce unnecessary muscle breakdown. Carbohydrates are the priority here since they are most directly tied to maintaining performance and glycogen levels as workouts get longer or more intense. Still, it’s worth considering whether protein or fat intake plays a role too.
Next, let’s look at how these effects differ between types of training, such as resistance and endurance exercise.
Pre-workout nutrition and its effects on different training styles
By now, it should be clear that both your overall diet and what you eat before training can influence how you perform at different intensities and durations. To see how this plays out, let’s look at a few studies that show how pre-workout nutrition affects performance in resistance, endurance, and mixed training.
Quick caveat: Before getting into the research, it’s worth noting why this topic can feel a bit more complicated than, say, post-workout nutrition. “Pre-workout” can describe a wide range of situations. Some studies involve people training after an overnight fast, while others examine participants who ate a full meal several hours earlier and are now consuming a smaller timed intake. Even among fed conditions, the timing, size, and composition of that meal can vary.
Because of that, the question isn’t only what to eat before training, but also when you last ate, how much energy you have available, and what macronutrients your previous meal contained. Those factors can all influence performance and are worth keeping in mind when looking at research or experimenting with your own routine.
Resistance training
For resistance training, the main questions are whether pre-workout nutrition can improve strength or volume performance and whether it helps preserve lean mass over time. Can lifters do more reps? Maintain load across sets? Reduce muscle breakdown?
Looking at the bigger picture, a systematic review by Henselmans et al found that eating more carbohydrates didn’t meaningfully improve resistance-training performance when total Calories and protein were the same. Across 49 studies, higher-carb diets rarely led to more total work performed, and getting enough protein (roughly 1.6–2.2 g/kg body weight) was still the most important factor for maintaining muscle.
That said, the review did note small benefits from timing carbohydrates around training, especially during longer or high-volume sessions, training fasted, or when Calories were restricted. In those cases, extra carbs did seem to help maintain performance.
Adding a little more to the data, a systematic review and meta-analysis by King et al looked at 21 controlled crossover trials and found that pre-workout carbohydrates improved total training volume when sessions lasted longer than 45 minutes or involved more than 8-10 sets. In short, carbs might matter more when workouts are longer or more demanding. However, newer research from the same group suggests that context plays a big role. In trained lifters doing upper-body workouts after an overnight fast, a high-carbohydrate meal two hours before training didn’t improve performance compared to a low-carbohydrate meal, or even a low-Calorie placebo.
Looking at protein intake specifically, a 2025 meta-analysis by Casuso and Goossens looked at five randomized controlled trials to see whether protein ingestion before or after training improved exercise-induced adaptations. The results showed no meaningful difference in lean mass. There was a tiny bump in leg strength (based on two small studies) when protein was consumed before training. As discussed in detail in our article on protein timing, research shows that there are no small “anabolic windows,” which again aligns with the importance of total daily protein intake.
Resistance training takeaways
Training duration is still the biggest factor influencing whether pre-workout nutrition makes a difference. For most lifters who eat enough protein and Calories, strength and muscle usually do fine.
While both can be affected by extended energy restriction, it generally takes being underfed for longer periods to make an impact. That’s why it’s worth paying attention to your strength during a deficit. So, if you’re training fasted and hitting higher training volumes, you might want to eat something before training to see if it helps.
Pre-workout nutrition doesn’t make or break strength or hypertrophy outcomes, but it could provide small situational benefits. Keep that in the back of your mind for later when we’ll talk about readiness and training comfort.
Endurance and interval training
As discussed, glycogen use during resistance training is relatively modest, so pre-workout meals tend to have less impact on performance. In endurance or interval workouts, glycogen demands are higher, and availability can become an actual limiting factor. So let’s look at what the research shows.
A systematic review and meta-analysis by Aird et al examined 46 studies comparing fasted and fed exercise to see if a pre-exercise meal affects performance. The result? Carbohydrate-dominant meals consumed 1 to 4 hours before exercise improved performance. Specifically, it helped performance lasting longer than 1 hour.
Protein- or fat-heavy meals did not have the same impact on performance. Additionally, the dose of carbohydrates in this study definitely mattered. Intakes below about 1g of carbohydrate per kilogram of body weight had minimal effect, while higher doses had more of an effect on performance. A narrative review by Rothchild et al published a little later found similar outcomes after examining more than 100 studies on pre-exercise nutrition.
A review by Stratton et al looked at those who consumed breakfast versus those who omitted it in endurance- and resistance-trained athletes who trained earlier in the day. Once again, they found that for longer-duration exercise lasting more than 60 minutes, consuming a carbohydrate-rich breakfast 1 to 4 hours before training improved performance compared with exercising fasted.
So, if you’re doing endurance training, you probably shouldn’t skip breakfast.
In fact, a randomized crossover study by Metcalfe et al found that even when total daily Calories were matched, power output dropped in people who skipped breakfast compared with those who ate it. The group that skipped breakfast also reported higher perceived exertion.
What about interval training?
Studies on interval training can be tricky because much of the research focuses on its role in fat loss or metabolic outcomes. Still, when you look at the broader body of work, a pattern appears showing that carbohydrate availability may matter more.
A recent 2025 study by Thomassen et al had people perform intense knee-extension workouts using one leg with full glycogen and one that was glycogen-depleted. The low-glycogen leg performed about 40% worse in the test. Strength didn’t drop, but the leg ran out of steam much sooner. That suggests glycogen doesn’t directly affect how strong you are, but it can affect how long you can keep working at a high level before fatigue sets in.
Looking at perimenopausal women, a small randomized crossover study by Kotopoulea-Nikolaidi et al looked at high-intensity interval work that alternated between about 85 to 90% of their maximum heart rate and easier active recovery periods. After finishing the intervals, they completed a test to see how long they could keep exercising before reaching exhaustion. The researchers found a slight trend toward higher work output and better mood after a high-carbohydrate meal compared with protein-based or fasted conditions.
Also, as a reminder, the earlier study by Clauss and Jensen showed that intensity can increase protein utilization, and we’ve seen other studies show increased glycogen demand during high-intensity interval training or CrossFit-style training sessions.
There are obviously wide ranges within interval training when it comes to intensity, length, and how depleted you are beforehand, but it’s worth considering these factors, especially if you’re doing extremely demanding sessions in a fasted state or during a long-term Calorie deficit. There’s also a pretty decent amount of evidence suggesting that as high-intensity performance increases, glycogen can start to play more of a role.
Endurance and interval training takeaway
Overall, research shows that eating carbohydrates before exercise helps support endurance performance, especially when workouts last longer than an hour. In trained athletes, restricting carbohydrates lowers glycogen stores, which can, in turn, reduce performance in endurance or interval sessions that rely on glycogen for fuel.
A quick look at factors like satiety or habits
There are additional factors beyond fuel utilization that can influence pre-workout nutrition decisions, even if they’re not completely understood just yet, ranging from satiety to habitual factors.
The King study discussed earlier compared a very low-Calorie (2.6 Calories) placebo with low- and high-carbohydrate pre-training meals in trained lifters. While total training volume was similar across conditions, (not surprisingly) people reported more fullness and less hunger after a Calorie-containing meal. This suggests that eating something before lifting helps, but what you eat may matter less than simply being fed.
A study by Naharudin et al adds another layer by testing whether the texture of a pre-exercise meal matters. They compared a semi-solid placebo with a thinner carbohydrate drink, and found that the semi-solid placebo helped lifters complete more repetitions.
Habits may also play a role, as one study found that skipping breakfast before a morning resistance session impaired performance in people who normally eat breakfast. Overall, breakfast omission doesn’t appear to harm resistance performance for most lifters, but when it does matter, it matters a lot for that individual.
Altogether, these findings suggest that if you feel fed or more comfortable going into training, it can make a difference. Any performance or strength advantages seem small, but they appear often enough in research to be worth noting, with the caveat that “responses vary.”
| Consideration and questions for determining if your training demands specific pre-workout nutrition | ||
|---|---|---|
| Consideration | Description | Practical takeaway |
| Overall energy intake | Are you in an ongoing Calorie deficit or following a diet that depletes glycogen? | The lower your glycogen stores, the more important pre-workout carbohydrate intake becomes. |
| Time since last meal | How long has it been since your last meal or carbohydrate intake? | If it’s been several hours, a pre-workout carb source could help maintain performance. |
| Type, intensity, and duration of activity | Are you doing strength, power, or endurance work? High or low volume? Engaging in repeated glycogen-depleting rounds? | Longer or higher-volume, higher-intensity sessions benefit more from pre-workout carbs than shorter, low-volume sessions. |
| Psychology and satiation | How full or comfortable do you feel entering your training session? Are you easily affected by perceived hunger? | Eating before training could relieve feelings of sluggishness or improve focus. |
| Age, recovery, or injury status | Are you over 50, managing an injury, or dealing with slower recovery between sessions? | Older adults and those in recovery could benefit from including protein and carbohydrates closer to training. |
Putting this together for pre-workout nutrition considerations
Most people don’t need a complex pre-workout nutrition plan. These guidelines are meant to be flexible ranges, not strict rules, and are taken from the collective of the research we’ve been discussing.
Strength and resistance training:
- In short or moderate sessions, carbohydrate intake is rarely a limiter for performance.
- For high-volume training sessions, pre-workout carbohydrate intake may improve performance.
- Ideally, all trainees should hit their total daily protein (1.6-2.2g/kg/day) and have a balanced diet of macronutrients.
- Optional: Eat a small meal or snack before training to help with readiness and energy during exercise.
Hypertrophy or hybrid training:
- Carbohydrate intake could matter more for sustaining training quality and volume.
- Ideally, all trainees should hit their total daily protein (1.6-2.2g/kg/day) and have a balanced diet of macronutrients.
- Optional: A pre-workout meal containing about 0.5g/kg carbohydrate and 0.3g/kg protein, eaten 1-3 hours before training, could support performance.
Endurance training:
- Performance depends more directly on carbohydrate availability.
- Meet total daily protein (1.6-2.2g/kg/day), balanced diet, and Calorie needs.
- Ideal: Carbohydrate-rich meal (1-4g/kg) 1-4 hours pre-training seems to improve endurance performance. Adding 0.3g/kg of protein could help preserve muscle during longer sessions.
A quick note on whole foods versus supplementation
One aspect we haven’t covered yet is the difference between using whole foods and food supplements for pre-workout fueling. Many studies rely on liquid carbohydrate sources because drinks make it easier to deliver them. For example, most trials in the Aird review used glucose or maltodextrin drinks, while a smaller number included whole-food meals.
However, that doesn’t mean whole foods are off the table. In real-world settings, most people eat mixed macronutrient meals before training. A narrative review by Naderi et al compared traditional foods with supplements and found that when they matched total carbohydrates, the performances were pretty much the same. That said, the authors noted practical considerations, such as higher-fiber foods being harder to digest before training and generally being less portable. For that reason, liquid or semi-solid options are the common choice for most people.
In short, experiment with different meal types and timing to see what feels and performs best for you, as workout nutrition can be highly individual, especially in terms of readiness and comfort.
Closing
Endurance and some styles of intensive interval training are cases where pre-workout nutrition can truly move the needle. When a session runs long or the intensity stays high, carbohydrate availability becomes a more limiting factor for performance. In these instances, a well-timed meal or snack (with carbohydrates and maybe a little protein) could help maintain performance and might protect muscle.
Most of the pre-workout nutrition debate falls in that middle ground where the workouts aren’t easy, but the duration or intensity isn’t high enough to fully drain you. In these situations, the need for specific pre-workout nutrition mostly comes down to individual preference. However, it’s still worth experimenting to see whether it makes a difference for you. As long as it’s digestible and comfortable, it’s worth trying.
In the next article, we’ll look at what happens once training begins and how intra-workout nutrition fits into the picture.
