What to Eat an Hour Before a Workout

A small, carbohydrate-rich meal or snack eaten about an hour before exercise gives most people the best combination of available energy and stomach comfort. Think a banana with a thin layer of nut butter, a bowl of oatmeal with fruit, or a slice of toast with jam. The details matter more than you might expect, though, because what you eat in that narrow window affects how fast your stomach empties, how your blood sugar behaves in the first minutes of exercise, and whether your gut cooperates or rebels once the intensity climbs.

Why Carbohydrates Are the Priority

Your muscles run primarily on stored carbohydrate (glycogen) and blood glucose during moderate-to-hard exercise. Fat contributes fuel too, but carbohydrate is the only macronutrient that can power high-intensity efforts. An hour before a workout, the goal is to top off blood glucose and give your liver a small reservoir to draw from without leaving a heavy load sitting in your stomach.

Carbohydrate-heavy foods leave the stomach faster than protein or fat. An MRI study comparing standard meals found that a high-carbohydrate meal reached its half-emptied point in roughly two hours, while a high-fat meal took over three hours and a high-protein meal fell in between.¹ Those were full-sized meals, not pre-workout snacks, but the pattern holds at smaller portions: carbs clear out first, protein next, fat last. For a one-hour window, that ranking is everything. You want fuel that has mostly left your stomach and entered your bloodstream by the time you start moving.

Even among liquids, the composition matters. A crossover study testing different drinks found that a low-calorie blackcurrant juice emptied in about an hour and a half on average, while a higher-fat oat drink took closer to two and a half hours.² The practical takeaway: if you are drinking your pre-workout calories, keep fat content low and avoid thick, calorie-dense smoothies unless you have more than an hour to spare.

The Glycemic Index Question

You have probably seen advice to choose “slow-burning” carbs before exercise. The idea is that low-glycemic-index foods like oats, lentils, or sweet potatoes release glucose gradually, keeping blood sugar steady and sparing muscle glycogen so you can go longer. The original study behind this claim found that trained cyclists who ate lentils an hour before riding lasted about 20 minutes longer than those who ate potatoes.³ That is a large difference, and it sparked decades of follow-up research.

The follow-up research is mixed. One meta-analysis concluded that endurance performance was meaningfully better after a low-glycemic pre-exercise meal.⁴ But another systematic review and meta-analysis, looking at similar data with slightly different methods, found no clear performance benefit from low-glycemic meals before exercise, regardless of whether athletes also took in carbohydrate during the workout.⁵

What does that conflict mean for you? Practically, the difference between eating oatmeal versus a white bagel an hour before your workout is probably small for most people doing sessions under 90 minutes. If you are training for a marathon or an extended cycling event, there is a reasonable case for leaning toward lower-glycemic carbs. For a 45-minute gym session or a recreational run, whatever carbohydrate source sits well in your stomach is the right one. The best pre-workout food you never eat is worse than the imperfect one you always tolerate.

The Blood Sugar Dip That Catches Some People Off Guard

There is a real phenomenon that trips up a small fraction of exercisers: reactive hypoglycemia. You eat carbs, your blood sugar rises, insulin kicks in to bring it down, and then exercise starts pulling glucose into muscles at the same time. For some people, blood sugar drops low enough to cause shakiness, lightheadedness, or sudden fatigue in the first 15 to 20 minutes of a workout.

A large dataset of continuous glucose monitoring readings found that reactive hypoglycemia showed up in roughly 8% of exercise events on average, and fewer than 15% of individuals experienced it in more than a fifth of their sessions.⁶ The window most likely to trigger it was eating between about 30 and 90 minutes before starting, with a peak right around 60 minutes. That is exactly the timeframe this article is about, which is worth knowing.

Earlier lab work confirmed the pattern: when 20 subjects drank a glucose solution 45 minutes before exercise, half of them experienced blood sugar below the hypoglycemia threshold during the workout, while the other half stayed above it, and the difference was not explained by insulin sensitivity alone.⁷ A related study found that the people who dipped lowest tended to have a stronger insulin-secretion response to the glucose they consumed.⁸ In other words, some bodies just spike insulin harder, and those people are more vulnerable to the dip.

If you regularly feel terrible in the first 10 to 15 minutes of a workout after eating, this is likely what is happening. A few strategies can help: eat a bit earlier (two hours instead of one), pair your carbs with some protein or fat to slow absorption, choose lower-glycemic carbs, or simply push through, since the dip is transient and blood sugar usually corrects itself within 15 to 20 minutes as the liver releases glucose to compensate. It is uncomfortable but rarely dangerous for healthy people.

Where Protein Fits In

Protein is not the star of a pre-workout meal. Carbohydrate drives the acute fuel supply, and protein empties from the stomach more slowly, which can increase the chance of feeling heavy during exercise. But including a moderate amount of protein alongside your carbs has a couple of advantages worth mentioning.

First, protein before exercise raises circulating amino acid levels during the workout. A study comparing whey protein taken before versus after resistance exercise found that amino acid levels were elevated by about 50% following ingestion at either time, and net muscle protein balance shifted from negative to positive regardless of timing.⁹ The takeaway is that pre-exercise protein “works,” though it is not dramatically better than post-exercise protein for muscle building. If you are going to eat anyway, including some protein is a reasonable two-for-one.

Second, adding protein to carbohydrate before exercise may help with glycogen storage. Rodent studies have shown that a mixed carb-protein meal enhanced glycogen synthesis before exercise, and human studies have demonstrated faster glycogen resynthesis after exercise when protein is added to carbohydrate.¹⁰ Whether this translates to a noticeable performance boost in a typical gym session is debatable, but it is unlikely to hurt as long as you keep the portion small.

A practical portion might be a tablespoon of peanut butter on toast, a small container of Greek yogurt with berries, or a few slices of deli turkey rolled around a banana. You are not trying to hit a big protein target here. Roughly 10 to 20 grams alongside your carbohydrate is plenty.

What to Skip an Hour Before

Two categories of food consistently cause problems when eaten close to exercise: high-fat foods and high-fiber foods.

Fat slows gastric emptying dramatically. As the MRI data on meal composition showed, high-fat meals take nearly an extra hour to half-empty compared to high-carbohydrate meals.¹ That means a cheeseburger, fried food, or even a generous handful of nuts eaten 60 minutes before a workout will still be sitting in your stomach when you start. During exercise, blood flow shifts away from the gut and toward working muscles. With intense effort, gut blood flow can drop by 80% or more.¹¹ Food that has not emptied from the stomach when this happens has nowhere to go, and the result is nausea, cramping, or worse.

High-fiber foods pose a similar problem. Fiber slows digestion by design, and large volumes of indigestible plant matter can cause gas, bloating, and intestinal cramping once the gut starts losing its blood supply during exercise. A survey of endurance runners found that women running distances longer than 5 km were especially likely to avoid high-fiber foods before racing, reflecting the well-known association between fiber intake and lower-GI complaints during running.¹²

None of this means fat and fiber are bad in your overall diet. They are just poor choices in the 60-minute pre-workout window. Save the salad, the avocado toast, and the bean burrito for meals further from your training session.

When Eating Nothing Might Be Fine

Not everyone needs to eat before a workout, and there is a growing body of evidence that fasted exercise has its own metabolic advantages. Exercising without eating first leads to higher fat oxidation because insulin levels are low, which allows fat cells to release more fatty acids for fuel.¹³ Some researchers have argued this could drive beneficial adaptations in muscle mitochondria over time.

The trade-off is performance. A systematic review and meta-analysis found that eating before exercise improved performance in prolonged aerobic sessions (think runs or rides lasting well over an hour) but made no meaningful difference for shorter bouts.¹⁴ If you are doing a 30-minute strength circuit or a moderate jog and you feel fine on an empty stomach, there is no strong reason to force food. If your session is going to be long and hard, eating beforehand consistently helps.

Morning exercisers often end up in this category by default. You have been fasting overnight, and sometimes the choice is between eating something an hour early (which means waking up at 5 a.m. to eat before a 6 a.m. run) or just heading out the door. For shorter sessions, heading out the door is a perfectly reasonable option. For longer ones, even a small snack, like half a banana or a few crackers, gives your body something to work with.

Caffeine as a Pre-Workout Add-On

If you drink coffee or take a caffeine supplement before training, timing interacts with your food choices. The most studied protocol is consuming caffeine about 60 minutes before exercise, which lines up with peak blood levels for most people.¹⁵ But a study testing different pre-exercise supplement timings found that ingesting caffeine about 35 minutes before a fatiguing time trial appeared to be the sweet spot for performance improvement, possibly because it reduced how hard the effort felt.¹⁶

If you are eating an hour out and having coffee at the same time, that works for most people. If caffeine on a relatively empty stomach bothers you, eating first and having coffee 20 to 30 minutes later still puts the caffeine in a useful window. One thing to keep in mind: caffeine can speed gastric emptying slightly for liquids but may also increase stomach acid production, which is another reason pairing it with a small amount of food tends to sit better than taking it alone.

Training Your Gut to Handle Food Before Exercise

If you are someone who has always trained on an empty stomach and wants to start fueling beforehand, or if you have tried eating before workouts and had bad experiences, there is good news: your gut can adapt. A review of gut-training research found that gastric emptying can be improved, feelings of fullness can be reduced, and the risk of gastrointestinal distress during exercise decreases with deliberate practice.¹⁷

The approach is straightforward: start with very small amounts of easily digested food before low-intensity sessions, and gradually increase the volume and the exercise intensity over weeks. Your stomach and intestines learn to empty faster, absorb nutrients more efficiently, and tolerate the reduced blood flow that exercise brings.¹⁸ Endurance athletes who fuel during races routinely use this strategy in training, and it works for everyday exercisers too.

People vary widely in their gut tolerance, and some of that variation is just individual biology. If you have tried gut training and still cannot handle food within an hour of exercise, adjusting your timing (eating 90 minutes to two hours before) or relying on liquid calories instead of solid food can help bridge the gap.

How Heat Changes the Equation

If you exercise outdoors in summer or in a hot gym, your pre-workout nutrition deserves an extra layer of thought. Heat stress independently slows gastric emptying. A study comparing exercise in a hot environment (about 120°F) versus a neutral one (about 64°F) found that the volume of fluid emptied from the stomach dropped as core temperature rose, with a strong inverse correlation between rectal temperature and gastric emptying.¹⁹

The mechanism compounds what exercise already does. Blood flow diverts to the skin for cooling and to the muscles for work, leaving the gut with even less circulation than during exercise in comfortable conditions. The practical implication is simple: in hot weather, eat less before your workout, eat earlier, choose foods that empty faster (simple carbs, liquids over solids), and prioritize hydration. A sports drink or diluted juice may serve double duty, providing both fluid and a small amount of carbohydrate without sitting heavily in your stomach the way solid food would. Dehydration itself further impairs gastric emptying, so arriving to a hot-weather workout already behind on fluids makes everything worse.

Putting a Plate Together

Given all of the above, a practical one-hour-out meal looks something like this:

Base: 30 to 60 grams of moderate-to-low-glycemic carbohydrate, such as oatmeal, a slice of whole-grain toast, a banana, or rice cakes.
Optional protein: 10 to 20 grams from a source that is easy on the stomach, like yogurt, a few bites of chicken, or a scoop of whey in water.
Minimal fat: a thin spread of nut butter at most, not a handful of almonds or a slice of cheese.
Minimal fiber: this is not the meal for raw vegetables, beans, or high-fiber cereals.
Fluid: water alongside the food, roughly 8 to 16 ounces, adjusted upward if it is hot.

The portion should feel like a snack, not a sit-down meal. If you can still feel it in your stomach when the warmup starts, you ate too much or chose foods that are too heavy. Over time, paying attention to how different foods feel during your first set or first mile teaches you more than any general guideline. Use the science as a starting framework, then let your own stomach have the final word.