Work Out Before or After Breakfast: What to Eat

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

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by
Ashley Pitt, CPT, Pn1
— Signos
Fitness Writer
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Updated by

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Science-based and reviewed

Published:
April 16, 2024
April 26, 2022
— Updated:
November 30, 2023

Table of Contents

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 (HIIT), where your main goal is to Improve Performance or Gain Muscle, consider Eating Breakfast Before working out. This is called a “fed workout”.

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The Amount of Calories You Burn Won’t Change

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We’ve all been told that 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 fat.

Here’s why: Carbs are the fastest-acting macronutrient we consume, and the body uses carbs as its preferred fuel source.

How It Works: When we eat food containing carbs, our body breaks down the carbs into glucose, raising blood sugar. Insulin is then released from the pancreas 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, another hormone called glucagon stimulates the breakdown of glycogen into glucose, so it’s released back into the bloodstream for energy.

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

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

Benefits of Fasted Workouts (Exercising Before Eating)

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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 on an empty stomach first thing in the morning. Here are the benefits of fasted cardio:

Burn Fat

Working out when our glycogen stores are depleted makes our bodies begin to burn body fat for energy (known as fat oxidation). In other words, fat oxidation means we’ve used up any stored sources of glucose, but our body is smart enough to turn to another source of energy: stored fat.

Insulin usually inhibits fat breakdown (called lipolysis), while glucagon turns it up. During fasting, insulin is low, and glucagon is higher, promoting fat oxidation. This doesn’t necessarily mean you’re burning more calories, but you may be switching to fat as a primary fuel.

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 up to 24 hours after their workout. Both groups burned the same amount of calories, but those who exercised before eating burned more fat.

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 who worked out at other times during the day after meals.

The Intensity of the Workout Matters When You’re Fasting

Tip: Fasted low-intensity exercises like walking, yoga, or pilates may lead to more fat burning.

A meta-analysis of recent fasting studies found that low-to-moderate intensity aerobic exercise performed in the fasted state led to higher fat oxidation than a fed state.

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

Easier to Commit

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

Tip: Make working out the first item on your daily to-do list if you get sidetracked.

Regulate Blood Sugar Levels

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

Boost Metabolism and Improve Appetite Control

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

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 that something is not right. Consult your medical provider if you are concerned about this. You might find fed workouts our best for your body.

What Makes a Good Post-Workout Meal?

Eat 30 to 60 minutes after exercise. Aim for 15 to 20 grams of protein to provide the amino acids needed to Replenish Your Protein Stores and Build Muscle. Add complex carbs to Replenish Your Muscle Glycogen Stores. Here are some options you can try:

  • Plain Greek yogurt with berries and granola
  • Scrambled eggs with whole-grain toast
  • Protein smoothie almond milk (or even half chocolate milk), banana, spinach, almond butter, and chia seeds
  • Cottage cheese with blueberries and whole-grain crackers
  • Oatmeal cooked with egg whites and topped with peanut butter and chia seeds
  • Veggie omelet with whole wheat toast and a side of fruit

PSA: The post-workout meal is extra important if you choose to do a fasted workout, so this step shouldn’t be skipped.

Benefits of Fed Workouts (Eating Before Exercising)

Woman in the middle of a high-intensity workout

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 morning, 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.

2. Keeps 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 to fuel your workouts, your cortisol rises.

Why is Cortisol Important? High cortisol levels can suppress your metabolism or how many calories your body burns throughout the day, raise blood sugar, and promote fat storage.

Plus, depleting glycogen stores and switching to non-glucose energy sources can lead to fewer strength gains.

3. Hydration

Taking time to eat breakfast before your workout can improve hydration. Unless you’re an athlete or exercise for longer than an hour, most people don’t need to drink a sports drink. But, 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, so eating first thing may be a way to help.

Tip: If it’s hard to eat a full meal before your morning workout, eat something small, like a smoothie or oatmeal.

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. If your pre-workout meal contains healthy fat, ensure it’s not too much because fat takes longer to digest. Options include:

  • Overnight oats made with rolled oats, almond milk, and a scoop of protein powder
  • Whole grain toast topped with a hard-boiled egg
  • Greek yogurt topped with granola
  • Whole wheat wrap filled with turkey or chicken breast, lettuce, and tomato
  • Fruit smoothie with protein powder, almond milk, and banana
  • Whole grain cereal with milk and fresh berries
  • Baked sweet potato with a small serving of grilled chicken or turkey

Tip: If your stomach is upset from eating before exercise, try eating something different (or try a fasted workout!).

So, Should You Exercise Before or After Breakfast?

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Ultimately, the choice to exercise before or after breakfast comes down to you and your body. There are pros and cons with possible health benefits for both options. Some people may do better with fasted morning exercise, while others may feel better and more energized with some food in their stomachs.

Below are questions to ask yourself for each type of workout to help guide your choice:

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? Try early morning 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.

Tip: 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 that caused unintentional weight loss? 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.

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.

If you still aren’t sure what’s best for your body, working with a registered dietitian nutritionist (RDN) and a personal trainer can help you optimize your sports nutrition goals.

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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 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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