Should I Exercise on an Empty Stomach?

By Daniel Heller, MSc, CSCS, RSCC

Ever experience lightheadedness or mild nausea while working out? Those disorienting feelings may be linked to whether you ate before beginning your gym prep routine. This post is an invitation to really look at your exercise plan and answer for yourself if eating before exercising is right for you. A few key variables we’re going to explore are intention, intensity, duration, and the type of exercise. As with any drastic change in your health plan, be sure to consult your doctor to minimize the risk of potential negative effects of lifestyle changes.

Before we dive into answering the question of eating or not eating before exercising, let’s explore the difference between fasting and having an “empty” stomach. In research, “fasted” is the accepted term; “empty stomach,” on the other hand, is a feeling. In fact, it’s possible to have a full stomach and still to feel empty. A fasted state is usually the duration from when you go to bed to when you wake up ready to start your day. If you’re a morning exerciser, it will be a little bit easier to appreciate this distinction. In comparison to a fasted state, an “empty stomach” is a metaphor that suggests you’ve missed one or more meals.

Know your intention for exercising

Are you exercising for your health, athletic performance, body composition, and/or weight loss? If your intention is to burn fat, you might want to consider exercising on an empty stomach, but a specific intensity is required if you’re working at to achieve this goal. If your intention is to set a personal best on a run or a bike ride, exercising on an empty stomach may not be wise, as you might not have enough energy in the tank to maintain the intensity necessary to finish.¹

Subjectively rate your level of intensity. In the realm of exercise, intensity refers to the effort you’re putting into it. Intensity can also be measured using simple internal self-assessment tools to rate perceived exertion (see the intensity table below).² A few good suggestions for rating your perceived exertion are a numerical scale, a talk test, or a color scale. An example of a numerical scale would be 1-10, where 1 is no effort and 10 is maximum effort.  In the talk test, gauge your effort by being able to sing to only being able to do the exercise. Using a color scale, the rating is green-yellow-red, with green being minimum effort and red giving it your all.

Intensity Table

Intensity	Numeric	Talk Test
Low	1 2 3	Sing
Moderate	4 5 6 7	Talk
High	8 9 10	Can't talk

The question of whether or not to eat before you exercise can be answered by aligning your intention for exercising with your ability to effectively gauge your intensity using one of these scales. If you’re planning an exercise requiring a low to moderate intensity for less than 60 minutes, there’s no need to eat before. However, if your exercise requires a low to moderate intensity exceeding 60 minutes, you might want to consider having a little snack (i.e. apple with a tablespoon of peanut butter) an hour before your workout. If you’re planning on a moderate-to-high-intensity session greater than 45 minutes, consider having a larger snack (i.e. granola bar) 60 to 90 minutes before your workout.^1,3

In addition to determining the intensity you’ll be exercising at and for how long, consider the type of exercise. A lot of the information above comes from research done on aerobic exercise (cardio). But what about resistance training? General resistance training doesn’t require a huge elevation in heart rate, so a low aerobic intensity is usually what is experienced. This means that your body will be able to fuel your resistance training without a pre-exercise meal.⁴

A few caveats about exercising on an empty stomach: Research at this time does not support performing fasted workouts for the long-term goal of weight loss, as long-term effects have not been studied.³ Results from exercise science research is challenging to apply to everyday life because research environments are usually controlled with everything from meal composition, feeding time, and exercise mode(s) all predetermined. The drawback of not having a controlled environment is that it falls on your shoulders to address how you’re feeling energywise.

In a previous blog we discussed eating to fuel your physical activity. This blog went into detail about the impact of different macronutrients and the physical feelings associated with them. Choosing to eat before a workout is up to you—whether you accept or decline the invitation to see how you feel in both situations, a satisfied stomach or an empty stomach.

Until next time, live well and live active.

This content is not intended as a substitute for professional medical advice, diagnosis, or treatment. Individuals should always consult with their healthcare professional for advice on medical issues.

References:

Daniel Heller, MSc, CSCS, RSCC:   Holistic strength and conditioning coach, Daniel Heller, MSc, CSCS, RSCC earned his Bachelor’s of Science in exercise science and wellness from Bastyr University in 2009 on a direct path to having a positive impact in the world of exercise and sport science. Since graduating from Bastyr, Heller has gone onto coaching youth athletes in ice hockey, figure skating, and mountain biking. As well as developing postural alignment and compression garments with Oakley Inc. and was the primary author of the exercise chapter for the Metagenics FirstLine Therapy Patient Guidebook. In 2016, he received his Master’s of Science degree in Strength and Conditioning from the University of Edinburgh in Edinburgh, Scotland. Heller is continuing to coach and actively participates in the field of strength and conditioning.

Daniel Heller is a paid consultant and guest writer for Metagenics.