Few of us want to gain weight; and, frankly, that’s probably the big reason most of us exercise, even though we recognize that there are many other health benefits — including the positive impact exercise has on cardiovascular and metabolic health, muscle mass, sleep health, cognitive performance and emotional health (mood). And for years, we’ve heard that it’s important to eat something before exercise, and something after exercise, too; and that maybe carbohydrates are the best “pre-exercise” food. And yet, we’re also hearing a lot about the health benefits of carb reduction, not only for weight management, but for better glycemic control. So won’t eating more carbs before exercise make it harder to lose weight? The so-called advice you hear can be confusing; let’s see what the science says about what you should eat before a workout — and when you should eat it.

What kind of athlete are you?

Here’s some good news and some bad news. There are hundreds of ways to exercise, and all are good, albeit in different ways. Study after study point to the benefits of both aerobic exercise and resistance/strength training, whether it’s slow and long or short and high-intensity and spread over several intervals. Just moving, every day and in any way, is beneficial. (So, you really don’t have to be “an athlete” to have a lifetime involvement with exercise!) Variety in exercise is so beneficial that even top professional athletes are spending more and more time “cross-training,” in every which way imaginable, even though they’re likely only paid to excel at one sport. 

The problem is, there are so many different ways people exercise, with so much variability in duration, intensity, time of day… and there are so many different types of athletes (from mothers in their 30s who strength-train at a class three times/week, to male cyclists in their 50s who endure 5 long road-trips/week, to overweight men who walk an hour every other day) that scientists really have not yet compiled enough high-quality, controlled research to form definitive conclusions concerning the pros and cons of different dietary selections, quantities, and eating schedules for the various types of exercising groups. So it’s not only difficult to “generalize” about best eating/exercise plans, it’s also quite likely premature and irresponsible to do so, even though you can find dozens of healthcare blogs that claim to have definitive one-size-fits-all answers.  

Our point is this: The way you eat and the way you exercise is and actually needs to be “personalized” because it depends upon (1) the type of athlete you are, (2) your goals and desired outcomes, (3) how much time you can dedicate to working out, (4) what level of exercise intensity suits you, (5) what time of day you can work out, (6) what your sex, age and health status are and (7) what kinds of foods your particular body responds well to before, during and after exercise. And those are just some of the variables that are at play!

Therefore, the following general guidelines are just that — general. But we’ll explain, along the way, what findings the science is currently leaning toward and what previous claims are starting to come under doubt.

Eating before a workout is important …

Food is fuel. So what you’ve heard about the importance of eating something, some time before you exercise, is likely true. Athletic performance — especially in longer, endurance activities — is enhanced by eating within 4 hours of starting to exercise. Consuming fluids, 16 to 20 ounces of water, before you work out is also important for balancing fluid losses and improving the quality and length of recovery time, according to Cleveland Clinic. Plus, food and fluids counteract the negative effects of exercising on an empty stomach, which might include feeling light-headed, getting a headache, feeling faint, or in the worst case experiencing hypoglycemia (suddenly low blood sugar). 

The “general recommendation” by most leading organizations, such as the American Heart Association and the Academy of Nutrition and Dietetics, is to eat between one and four hours before you exercise. However, knowing that that’s not really feasible if you exercise early in the morning, these same experts suggest breakfast at least an hour prior to exercise and/or a small snack about 30 minutes prior to starting your activity. The exact timing does not appear to be important: a recent research review could not correlate any meaningful different effects from the timing of the pre-exercise “mini-meal,” whether it was consumed 15, 45, or 75 minutes before exercise.

… But eating too much reduces health benefits

Contrary to these generalized “eat before you exercise” recommendations, scientific research has actually firmly established that performing low-to-moderate intensity exercise in an “overnight-fasted state” can induce higher levels of fat oxidation (“burning”) compared with exercise performed following ingestion of food, and especially of carbohydrate-rich foods — with less of a difference in fat oxidation levels as exercise intensity increases. In other words, eating prior to exercise may enhance the performance of endurance athletes, like marathon runners,  cyclists or powerlifters, but for those of us doing shorter-duration exercise regimens, there’s a price we pay for eating before (and after) a workout: we might not burn as much fat or have as easy a time managing weight — especially if we eat a higher-than-needed quantity of food before exercise.

This begs the question, do you even need to eat if you are exercising at moderate intensity and for a relatively short duration? Exploring that issue, scientists reported in a 2021 randomized controlled clinical study that there were no significant differences in athletic performance between a group of men that fasted before a high-intensity interval training (HIIT) session and a group who first ate a carb-rich breakfast. And the fasted group didn’t report more hunger or weakness, either. As it’s quite possible that these HIIT sessions, which the study authors called “moderate intensity,” may have actually required much more overall exertion than, say, a one-hour walk or a fitness class, we have to wonder if skipping breakfast before low-intensity, short-duration exercise would really make much of a difference. 

Similarly, in a small 2018 study of overweight men who walked for 60 minutes at 60 percent maximum oxygen consumption, the group of them that fasted prior to the exercise regimen not only had a higher level of fat oxidation and lower blood glucose levels than the group fed two hours prior to walking, but — at the gene expression level — the fasted group scored better relative to their “adipose tissue response,” a key marker of health. This led the authors to propose that “feeding before exercise blunts some of the health-related changes [i.e., benefits] induced by exercise training.”

Eating before a workout: moderation and portion control 

Taking into account the pros and cons of eating or not eating prior to exercise, and assuming we’re neither highly-trained top athletes nor sedentary, overweight couch-potatoes, eating before exercise — but “just enough” — seems to be the safest and most beneficial recommendation. Over-eating prior to exercise is not only associated with the aforementioned “blunting” of the positive health benefits of exercise, but it can also bring on gut discomfort in some individuals.

“Just enough,” of course, is not an easy quantity to identify, and there are numerous personal and health-related variables to consider. But since medical experts have long asserted, and few dispute, that restricting overall caloric consumption is essential for weight management, “portion control” — whether you’re eating before exercise, after, or at any time of day, for that matter — is still at the heart of all healthy dietary strategies. We’ll talk more about quantity after first discussing the quality, or the types, of foods that are considered optimal when working out.

Should you eat carbs before a workout?

Most leading medical organizations, such as Mayo Clinic, advise all of us to “focus on carbohydrates for maximum energy” during that 4-hour window prior to exercising, and especially in the 1-hour window just before. This recommendation stems from decades of research that showed how athletic performance improves following pre-exercise carb ingestion. However, as reported in a 2020 meta-analysis of all the better clinical studies on the subject, that performance boost was only well-documented in long-term, endurance training exercises. “Carb-loading” does not demonstrate the same benefits in moderate-intensity, short-duration exercise, the scientists theorizing that this relates to the complex science of “mitochondrial signaling” and other factors.

In fact, the 2021 study we referenced earlier was one of the first of its kind to compare continuous exercise and HIIT performed in the overnight-fasted state with both carbohydrate-rich and protein-rich pre-exercise meals. Their data revealed that pre-exercise protein ingestion allowed for similarly high levels of fat oxidation as pre-fasting, with athletic performance comparable to the group fed a carb-rich breakfast, at least for activities of relatively short duration. (The authors did admit, however, that gut discomfort was modestly higher in the protein group.) 

Their conclusion is worth noting: all three eating regimens “are viable choices as performance was not compromised, suggesting athletes can choose whether to eat based on personal preference.”

“Personalized eating” and finding your carb/protein balance 

The aforementioned studies are starting to question whether eating a high-carb meal before exercising is right for all of us. The premise: if you’ve fasted overnight, or had a light meal early in the evening before (rather than a big meal late at night), and you don’t overdo the carbs right before exercise the next morning or day, you may have a greater chance of improving your fat/lean-mass body composition — if that is your goal. (See our report, Confused About Carbohydrates?, to learn more.) When glycogen and circulating glucose levels are low, active tissues use fat from storage. The trade-off: your intensity level or endurance might be lower if you restrict carbs prior to exercise. 

Therefore, the most balanced approach, put forth by leading medical organizations, is to eat a small, balanced meal both before and after exercising. By balanced, we mean both carbs and proteins, and minimal healthy fats (prior to the workout), as the latter can cause a bit of gut discomfort (for some people, not all) during exercise. Carbs help you power through a longer training session, while protein helps slow the infusion of glucose (in order to help prevent an insulin spike and a too-rapid rise in glucose). After your workout, protein helps you build muscle and carbs rich in fiber ensure that you have a continuous flow of fuel. Thus, the old notion that you should eat all carbs before exercise, and drown yourself in protein after exercise, is now ill-advised. 

Eating before exercise:
Your small meal (on average, two hours prior to exercising, but no sooner than 30 min. before or longer than 4 hours prior) might best include a 3:1 ratio of carbs to lean protein, with total calories of about 200-250. A low amount of healthy fat is OK, but don’t overdo it, as fats (and some high-fiber carbs) can upset your stomach during a workout. 

Suggestions:

• A banana and peanut butter
• A protein bar that has a good source of carbs
• An egg with whole-grain bread and jam
• Low-fat Greek yogurt with granola and some berries
• Oatmeal and a few almonds

Eating during exercise:
Depending on the intensity and duration of your exercise routine, a rapidly absorbed source of carbohydrates during your workout could prove a beneficial addition to the food/fuel you consume prior to exercising. But if you don’t exercise over a long, intense period, refueling with carbs (especially if they are simple sugars) is not going to be necessary — and, in fact, could derail your weight-management goals. However, water/hydration during exercise is a must: see our report on Dehydration.

Eating post-workout:
After an intense workout, your body does benefit from a moderately higher quantity of lean protein, ideally within 30-60 minutes, but also again 2-3 hours later, to help restore amino acids and build muscle mass. However, you don’t need to overwhelm your body with the majority of the day’s protein immediately following a workout! In addition, carbs are important to refuel the glycogen stores, and the insulin produced by carb consumption acts as an anabolic agent to help with protein synthesis. Healthy fats — vitally important for reducing risks of cardiovascular disease, diabetes, and some cancers — can and should be consumed in moderation any time of day, but preferably following — rather than immediately before — your exercise regimen.

Suggestions:

• Chocolate milk
• String cheese and a handful of whole wheat crackers
• Fresh chicken and avocado whole wheat bread sandwich
• Peanut butter on apple slices
• Swiss cheese and vegetable wrap

Sources: Cleveland Clinic, Mayo Clinic, January AI

Key Takeaways

Wouldn’t you know, when it comes to meal-planning, it all comes down to balance and moderation — even when taking exercise into account. Unless you are a high-performance athlete, or an individual with a serious medical condition — both of whom may be following a strict dietary and exercise regimen designed just for their condition and goals, you’re best off following a dietary plan that includes a small, balanced meal (with a good proportion of healthy carbohydrate foods, but also lean protein) about an hour or so before exercising; hydration during exercise; followed by another small, balanced meal after your workout that emphasizes a moderately higher proportion of lean proteins, but also includes carbs and healthy fats. The importance of consuming carbohydrates before exercise probably increases as the exercise intensity and duration increases. Portion control and a balance of nutrients are key, and you need to experiment with what works best for you given your activities, intensity, time and particular metabolic tendencies.