Eating Before Workouts: Yay or Nay?

By: Dr. Clay Moss

If you’ve spent any time in the health and fitness world, you’ve probably heard both sides.

“You need to eat before you work out.”

“Fasted workouts burn more fat.”

So which one is right?

Both can be.

The better question isn't “Should I eat before I exercise?” It’s “What am I trying to get out of this workout?”

Because a 30-minute morning walk and a 90-minute hard training session are not the same thing. And they probably shouldn’t be fueled the same way. For most people, especially busy parents trying to stay healthy, strong, and fit, the goal shouldn’t be to obsess over the perfect pre-workout meal. The goal is to fuel when fuel actually helps.

When Fasted Workouts Make Sense

When you exercise without eating beforehand, insulin is generally lower and your body tends to rely more heavily on stored fat for energy. That doesn’t automatically mean you’ll lose more body fat.

This is an important distinction.

Burning more fat during one workout is not the same thing as losing more body fat over the course of several months.

Your overall diet, calorie intake, activity level, muscle mass, sleep, and consistency still matter much more. But there can still be reasons to train fasted.

For lower-intensity workouts, your body usually has more than enough stored energy to get the job done. Think walking, easy cycling, Zone 2 cardio, an easy 30 to 45-minute run, or a shorter, lower-volume workout.

If you wake up, have some water or electrolytes, and feel great exercising before breakfast, there’s usually no need to force food down just because someone told you that you “need fuel.” Your body already has fuel.

You have stored fat. You have liver glycogen. And importantly, you still have muscle glycogen left over from the food you ate the day before. An overnight fast does not mean your muscles suddenly wake up with an empty gas tank.

For these easier workouts, training fasted can also be a useful way to maintain your body’s ability to efficiently use fat as an energy source.

When You Should Probably Eat

There is another side to this.

As the intensity or duration of exercise increases, carbohydrates become increasingly valuable. Your body can produce a lot of energy from fat, but it cannot produce that energy nearly as quickly as it can from carbohydrates. That matters when you’re asking your body to perform.

Hard interval training, sprint workouts, high-volume strength training, difficult leg days, tempo runs, long-distance running or cycling, and workouts lasting 75 to 90 minutes or longer are all situations where eating beforehand may be more useful.

These are workouts where the goal is usually not simply to “burn calories.” You’re trying to run faster, lift heavier, complete more quality reps, or maintain a higher workload. In that situation, eating beforehand can improve the quality of the workout. And workout quality matters.

If eating some carbohydrates allows you to run faster, get two more productive sets in, or maintain your pace during the second half of a long run, that may be far more valuable than simply being able to say you trained fasted.

A Simple Rule

Easy workout? You probably don’t need to fuel it.

Hard workout? Fuel can help you perform.

What About Strength Training?

This one gets overcomplicated.

If you had a normal dinner the night before and you’re lifting weights first thing in the morning, your muscles probably still have plenty of glycogen. So no, you don’t necessarily need a giant bowl of oatmeal before a 45-minute strength-training session.

Some people train great fasted. Others feel noticeably stronger after eating. Both are fine.

Where carbohydrates becomes more useful is when the workout gets particularly demanding. High-volume bodybuilding workouts, long leg sessions, multiple workouts in one day, training after another glycogen-depleting workout, or training while eating very low carb are all situations where a little carbohydrates beforehand may improve performance.

Protein is also worth considering. If it has been a long time since your last meal, having 20 to 40 grams of high-quality protein before training is a simple option.

But there is no five-minute “anabolic window” you need to panic about. Your total daily protein intake and consistently eating adequate protein matter far more than whether your protein shake happens at 7:45 or 8:30.

What Should You Eat Before a Workout?

If you choose to eat, the best pre-workout meal is usually pretty boring. And that’s a good thing.

You generally want protein plus easily digested carbohydrate.

You usually don’t need a massive meal loaded with fat and fiber right before exercising. Fat and fiber are great parts of a healthy diet, but they also slow digestion, which is not always what you want before running, jumping, squatting, or doing burpees.

If you have two to three hours before training, something like Greek yogurt with berries and honey, eggs with fruit and toast, chicken and rice, oatmeal with fruit and protein, or lean protein with potatoes can all work well.

If you only have 30 to 60 minutes, keep it simpler. A banana, fruit with whey protein, a little honey, a couple of dates, a small amount of juice, or an easily digested carbohydrate drink may be all you need.

The closer you get to your workout, the easier the food should generally be to digest. You do not want to discover halfway through a run that your “high-fiber superfood breakfast” is still sitting in your stomach.

What About Long Cardio?

This is where fueling becomes much more important. If you’re going for a 30-minute jog, you probably don’t need carbohydrate. If you’re going out for a two-hour run, that’s a completely different situation.

Once exercise starts getting past roughly an hour, particularly if it’s moderately hard, you should start thinking more seriously about carbohydrate (there is debate regarding people who are truly “fat adapted” in a ketogenic diet needing less intra-workout carbohydrate than others, but that is for another day).

For longer endurance training, carbohydrate before and sometimes during exercise can help you maintain performance and delay fatigue. For many recreational athletes, 25 to 60 grams of carbohydrate per hour during longer exercise is a reasonable starting point.

The longer and harder the event, the more important fueling becomes. This is why trying to prove how “metabolically healthy” you are by doing every long run fasted can actually become counterproductive. Sometimes the healthiest thing you can do is simply give your body the fuel required to perform the workout you’re asking it to perform.

Don’t Confuse Fasted Training With Fat Loss

This deserves repeating.

Fasted exercise can increase the amount of fat you burn during that workout. But that does not necessarily translate into dramatically more body-fat loss over time.

If fat loss is your goal, the fundamentals still win. Adequate protein, strength training, daily movement, mostly whole foods, good sleep, a reasonable calorie intake, and consistency are all going to matter much more. Whether you ate a banana before your workout is pretty far down the list.

The Strategy I Prefer

Instead of choosing between “fasted training” and “fed training,” use both. Think of fueling as another tool. Some workouts are great opportunities to train your body’s ability to use stored energy. Other workouts are opportunities to maximize performance.

A morning walk or easy Zone 2 session can easily be done fasted if you feel good. A normal 45-minute strength workout can go either way. A hard leg day, interval run, or long Saturday run is probably a better place to bring in protein and carbohydrate.

You don’t need to turn breakfast into a science experiment. Just match the fuel to the demand.

The Bottom Line

You do not need to eat before every workout. And you do not need to train fasted to prove that your metabolism is working. Instead, ask yourself one question: What is the goal of today’s workout?

If you’re doing an easy session and feel good without eating, training fasted is completely reasonable. If you’re trying to maximize strength, speed, training volume, or endurance, eating beforehand may help you get more out of the session.

My favorite way to think about it is simple: Don’t spend carbohydrate on workouts that don’t need it. But don’t withhold carbohydrate from workouts where it allows you to perform substantially better. Your nutrition should support your training, not make it more complicated.

Dr. Clay Moss is a licensed medical doctor completing formal training in Physical Medicine & Rehabilitation. 

This article was reviewed by Rosie Borchert, NASM-CPT, for accuracy.