Should You Exercise Before or After Breakfast?

Ashley Pitt, CPT, Pn1, helps you choose between fed and fasted morning workouts based on your performance and weight loss goals.

A man and woman doing lunges in a park just after sunrise

Should you eat before or after a morning workout? It depends. 

  • For low-intensity exercise where your main goal is to burn fat, consider working out before you eat breakfast. This is called a “fasted workout”.
  • For high-intensity exercise where your main goal is to improve performance or gain muscle, consider eating breakfast before working out. This is called a “fed workout”.
person running on trail at dawn

The Amount of Calories You Burn Won’t Change 

We’ve all been told that in order to lose weight we need to be in a caloric deficit. But, weight loss is more than caloric deficit. In fact, you can burn the same number of calories by working out before or after eating, but you will burn different amounts of fat1.

Here’s why.

Carbs are the fastest-acting macronutrient that we consume, and the body uses carbs as its preferred source of fuel2.

<p class="pro-tip">How it works—When we eat food that contains carbs, our body breaks down the carbs into glucose. Insulin is then released from the pancreas in order to help shuttle the glucose into our cells, where it can be used for energy. Excess glucose gets stored in the liver and muscles as glycogen. When blood sugar levels drop, glycogen is broken down into glucose and released into the bloodstream for energy.</p>

However, the body doesn’t store glycogen for long. When fasting, such as during sleep, liver glycogen is broken down to release glucose into the bloodstream to be used by other tissues, such as the brain. Muscle glycogen is only broken down during periods of intense physical activity to provide additional energy to muscle cells.3

When liver glycogen stores are depleted, the body starts to convert fat and protein to energy. This is called gluconeogenesis; the basis of fasted workouts.

Benefits of Fasted Workouts (Exercising Before Eating)

A fasted workout is where you abstain from all food and drink other than water, for anywhere from eight to 12 hours before a workout.

Fasted cardio is low-intensity steady-state cardio performed first thing in the morning; on an empty stomach. Here’s the benefits of fasted cardio: 

1 - Burn fat

By working out when our glycogen stores are depleted, our bodies begin to burn fat for energy. 

You burn more fat when exercising before breakfast.

In one study of 10 healthy men, the group who exercised before eating breakfast (the other group worked out later in the day—after eating) showed increased fat oxidation for up to 24 hours after their workout. Both groups burned the same amount of calories, but the group who exercised before eating burned more fat.1

In another study of nine healthy females, those who exercised before eating breakfast—after fasting overnight—also showed an increase in fat oxidation for up to 24 hours after their workout, compared to those in the study who worked out at other times during the day after meals.4

The intensity of the workout matters when you’re fasting. 

According to one meta-analysis of recent fasting studies, the researchers found that low-to-moderate intensity aerobic exercise performed in the fasted state led to higher fat oxidation compared with a fed state. 

However, there was no significant fat oxidation difference between fasted and fed states during moderate-to-high intensity aerobic exercise.3

A group of students practicing yoga in class.
Lower-intensity workouts before eating can burn more fat.

2 - Easier to commit

When you get straight to your workout before having breakfast, there’s less of a chance you’ll be derailed. 

<p class="pro-tip">Tip: Make working out the first item on your daily to-do list if you have a tendency to get sidetracked.</p>

3 - Regulate blood sugar levels 

Eating carbs can cause blood sugar levels to spike. By exercising before eating, we can burn off some of the glucose, help keep blood sugar levels in check, and reduce risk of insulin resistance.

<p class="pro-tip">Related reading: To find out more about insulin resistance, read this guide to insulin resistance and prediabetes.</p>

4 - Boost metabolism and improve appetite control

Exercise helps to increase our resting metabolic rate, which means that we burn more calories even when we are not actively working out. It’s beneficial for both weight loss and weight management.

<p class="pro-tip">PSA: Not everyone should do fasted workouts. If you feel dizzy, lightheaded, unwell, or extremely fatigued while working out fasted, your body is telling you something is not right. Consult your medical provider if you are concerned about this. You might find fed workouts are best for you.</p>

What Makes a Good Post-Workout Meal?

Eat 30 to 60 minutes after exercise. Aim for 15 to 20 grams of protein to replenish your protein stores. Add complex carbs to replenish your muscle glycogen stores. A protein shake with chia seeds is an easy option.

<p class="pro-tip">PSA: The post-workout meal is extra important if you chose to do a fasted workout, so this step shouldn’t be skipped.</p>

Man and woman drinking protein shake after workout
Related reading: To find out more about pre- and post-workout protein, read this article about timing protein intake.

Benefits of Fed Workouts (Eating Before Exercising)

A fed workout is where you eat or drink something with calories, within four hours before a workout. Here are the benefits of fed workouts:

1 - Better Performance During Workout

Your metabolism keeps working overnight, and by the time morning comes, you are often slightly dehydrated and depleted. If you work out before eating breakfast, you won’t have as much energy available to perform at your best. 

Woman in the middle of a high-intensity workout

2 - Keep Cortisol Levels Under Control

Working out before eating might harm weight loss efforts. According to the National Academy of Sports Medicine, when your body resorts to gluconeogenesis in order to fuel your workouts, your cortisol rises

<p class="pro-tip">Why is cortisol important? High cortisol levels can suppress the amount of calories your body burns throughout the day. When you begin converting other macronutrients to fuel, you can deplete your glycogen stores, leading to less strength gains.5</p>

3 - Hydration

Taking time to eat breakfast before your workout can improve hydration. According to the American Council on Exercise, even small amounts of dehydration can negatively impact athletic performance. When you’re dehydrated, it’s easier to overheat, get tired, and develop cramps.6

<p class="pro-tip">Tip: If it’s hard to eat a full meal before your morning workout, eat something small, like a smoothie or oatmeal.</p>

What Makes a Good Pre-Workout Meal?

Try to eat two hours before you exercise. The best pre-workout meal can include complex carbs—think oats, legumes, or potatoes—and some protein. The carbs will provide the primary fuel source to help your body perform during your workout.

A bowl of oatmeal with blueberries.
Make sure your pre-workout meal is low in dietary fat (it takes longer to digest). 

<p class="pro-tip">Tip: If your stomach is upset from eating before exercise, try something different (or try a fasted workout!).</p>

Plan Your Morning Meal and Workout Timing

Reasons to exercise before eating breakfast:

  • For fat loss—Are you trying to lean out and lose fat? Exercise before and eat breakfast after to support fat oxidation.
  • For busy mornings—Is your morning jam-packed, but you still want to move? Exercise before and eat after to save time.
  • For low-intensity exercise—Do you plan to do yoga, low-intensity steady state cardio or something on the lighter side? Exercise before and eat after.

Reasons to eat breakfast before exercise:

  • To enhance performance—Are you training for a sporting event or an event that requires you to perform at your peak? Eat breakfast before exercise to support performance. If you are preparing for an event or need to boost your performance, try eating a carbohydrate-rich meal about two hours before your first workout of the day to help you reach new personal records.
  • To build lean muscle—Are you trying to build your muscles in a hypertrophy phase? Eat breakfast before exercise to support strength gains.
  • To gain body mass—Are you underweight or recovering from an illness in which you lost a lot of weight? Eat breakfast before exercise to support weight gain.
  • For long workouts—Are you planning to work out for more than an hour? Eat breakfast before exercise to support endurance and energy levels.

<p class="pro-tip">Tip: It’s okay to adjust your approach as needed to keep up with your changing schedule, goals, and lifestyle. You can incorporate both fed and fasted workouts throughout your week to maximize your results. If this works, try structuring your week with a couple of days of fasted low-intensity steady-state workouts. Save more intense workouts for days when you have a pre-workout meal.</p>

Person drinking coffee while looking at phone.

Read next: To better understand your blood sugar, read this article on why your blood sugar can be high in the morning.

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References

  1. Iwayama, K., Kurihara, R., Nabekura, Y., Kawabuchi, R., Park, I., Kobayashi, M., Ogata, H., Kayaba, M., Satoh, M., & Tokuyama, K. (2015). Exercise Increases 24-h Fat Oxidation Only When It Is Performed Before Breakfast. EBioMedicine, 2(12), 2003–2009. https://doi.org/10.1016/j.ebiom.2015.10.029 
  2. Hargreaves, M., & Spriet, L. L. (2018). Exercise Metabolism: Fuels for the Fire. Cold Spring Harbor perspectives in medicine, 8(8), a029744. https://doi.org/10.1101/cshperspect.a029744 
  3. Murray, B., & Rosenbloom, C. (2018). Fundamentals of glycogen metabolism for coaches and athletes. Nutrition reviews, 76(4), 243–259. https://doi.org/10.1093/nutrit/nuy001 
  4. Iwayama, K., Kawabuchi, R., Nabekura, Y., Kurihara, R., Park, I., Kobayashi, M., Ogata, H., Kayaba, M., Omi, N., Satoh, M., & Tokuyama, K. (2017). Exercise before breakfast increases 24-h fat oxidation in female subjects. PLOS ONE, 12(7), e0180472. https://doi.org/10.1371/journal.pone.0180472 
  5. Comana, F. (n.d.). Breakfast and Fasted Cardio – Is it Really Worth it? NASM. Retrieved April 27, 2022, from https://blog.nasm.org/fitness/breakfast-and-fasted-cardio-is-it-really-worth-it 
  6. FitFacts - ACE. (n.d.). Retrieved April 27, 2022, from https://acewebcontent.azureedge.net/assets/education-resources/lifestyle/fitfacts/pdfs/fitfacts/itemid_173.pdf 

About the Author

Ashley Pitt's Headshot
Ashley Pitt is a NASM certified personal trainer, a group fitness instructor, a Precision Nutrition level 1 coach and the creator of the wellness and lifestyle blog, A Lady Goes West.
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Please note: The Signos team is committed to sharing insightful and actionable health articles that are backed by scientific research, supported by expert reviews, and vetted by experienced health editors. The Signos blog is not intended to diagnose, treat, cure or prevent any disease. If you have or suspect you have a medical problem, promptly contact your professional healthcare provider. Read more about our editorial process and content philosophy here.

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