“Should I Eat Before I Exercise?”

For as long as I can remember- from the first time I set foot in a gym, actually- I’ve been listening to folks debate the question…

“Should I eat before I exercise?”

Now a new study may finally shine some light on the matter. Researchers found that exercising on an empty stomach has several beneficial effects, including preventing weight gain and maintaining insulin sensitivity.

Researchers in Belgium took 27 healthy young men and fed them all a horrible diet, high in sugar and fat and calories. The particular diet was chosen because it was just about guaranteed to create both weight gain and a reduction in insulin sensitivity.

Insulin sensitivity, you may remember, is something good- it’s when the cells respond well to insulin, meaning that insulin does an excellent job of removing excess sugar from the bloodstream and getting it into the cells where it can be “burned” for energy. When someone is said to be insulin resistant on the other hand, this system doesn’t work well, and the person winds up with high blood sugar and high insulin and is on the path to either metabolic syndrome or diabetes. Most diabetics are insulin resistant, and most people who are insulin resistant are overweight, since insulin “shuts down” the fat burning process.

In the Belgian study, the researchers divided the men into three groups:

  1. One group did nothing but eat the terrible diet (the control group). This group didn’t exercise at all during the study.
  2. The second and third group did exercise, and did the exact same workout;
  3. but the second group did it after breakfast and the third group did it before breakfast, exercising on an empty stomach.

The results were both surprising and dramatic.

The control group- not surprisingly- gained a lot of weight and also saw their insulin sensitivity plunge (meaning they became much more insulin resistant). The “exercise after eating” group also gained weight, but not nearly as much as the control group. And their insulin sensitivity went down, just as it did in the control group.

But the “exercising on an empty stomach” group was a whole different story. This group- despite eating a perfectly horrible, weight-gain inducing diet- did not gain weight. Not only that, their insulin sensitivity remained high and the bad diet did not make them insulin resistant. “This study for the first time shows that fasted (empty stomach) training is more potent than fed training to facilitate adaptations in muscle and to improve…. glucose tolerance and insulin sensitivity…” said the study’s authors.

Conventional wisdom- which is not always so wise—has held that it’s always best to eat something before working out. Proponents of this way of thinking would always point out that you need “energy” for working out, energy which comes from—what else?—carbohydrates. “Fat burns in a flame of carbohydrate” they’d proclaim solemnly.

Problem is, the conventional wisdom is wrong.

It’s interesting that back in the days of “Stay Hungry” and “Pumping Iron” when the big meccas of bodybuilding like World Gym and Gold’s Gym in Venice were home to such legendary bodybuilders as Arnold Schwarzenneger, Lou Ferrigno and Franco Columbo, everybody exercised on an empty stomach. Bodybuilders of that era believed that you were more likely to mobilize your fat stores for fuel if you didn’t have to burn off a whole bunch of carbs that you just scarfed down for breakfast.

We now know that they were mostly right.

So should you forgo eating before working out? Not necessarily. “If you’re interested in performing better- like if you’re training for an event—you might want to eat first”, says my friend exercise physiologist Liz Neporent, MS, CSCS, author of “Fitness for Dummies”. “But for weight loss, evidence does seem to be trending towards not eating before working out”.

Neporent points out that as a practical matter, there are going to be a fair amount of people who don’t do well when they don’t eat before working out. “They get dizzy, sick, and even faint sometimes”, she told me. “But I’ve also had people eat right before working out that have felt exactly the same way!”

Bottom line, it’s going to be- like everything else- an individual thing and no one prescription is going to work for everyone.

But for those who want to try it- and who don’t get lightheaded or dizzy- exercising on an empty stomach might be just the thing to stop weight gain in its tracks. It did in the Belgian study, and those folks were purposely eating a really bad diet. It should work even better if you also couple it with a diet designed to help you reach your goals.

Watch this funny little video where I reveal my 5 favorite fat burning snacks that won’t trigger a high insulin response.




  1. Warren

    Did they describe the workout protocol? I’m interested to know if the results would be different between a more “energy systems” or “cardio” oriented workout vs strength training.

  2. Kathleen

    I’m one of those people who don’t do well without “a little something” on my stomach before a workout. I used to go to the gym at 5 AM with only a cup of coffee, until one day when I was forced to sit down. I was sweaty, nauseous and felt faint. Turns out, I was hypoglycemic and my insulin levels dipped too low.

    I’d say whether you need to eat depends on how long and how hard you’re working out. Back then, I did an intense 45 minutes of weight training followed by 45 minutes of moderate-to-intense cardio. No wonder I was nearly conking out!

  3. linda giampaolo

    Good Morning Jonny,

    I must admit that I am not convinced with this research. Many studies that I have read found the safest and most effective fuel before exercise is a small amount of CHO rich whole food, such as a bowl of berries. The brain need a little bit of CHO to transition our bodies into a fat burning mode. The same research led me to believe a hard workout after a night of fasting leads to increased muscle breakdown and less efficient fat burning? How wrong am I?

  4. Keren

    I notice that the study didn’t necessarily address having a small protein meal (as opposed to the high carb meal) before working out and I wonder if the results of that would have been similar to not eating before exercising. Can you possibly address this issue, please?

    Many thanks

  5. Gloria

    It was not indicated what exercise route they were doing and for what length of time. I do martial arts and I’ve learned I can not do that on an empty stomach nor a full one. If I am working out at home with a video I can do so before breakfast.

  6. Karen McCoy

    Thanks Jonny for setting the record straight. I did cardio on an empty stomach for years for fitness contests, and it made all the difference in the world. I would challenge any of these ‘study gurus’ to test the water themselves….there’s proof in that pudding, but you gotta try it yourself. Arnold, Franco and co. were truly right.

  7. Mark

    Great article Dr. Bowden! I’ve been doing fasted training (except 10 g or BCAA and 5 g creatine 10 minutes before) to fantastic success. While this study was done with “endurance exercise”, I have had no problems with weight training, even up to heavy singles. Thanks again for the great information!

  8. Brenda

    I have a thought………… I wonder what would happen in a study like this if there was one group who only ate protein or non-carb foods before a workout…………could they react the same as the ones in the “no food” before exercise group or differently?

    And I want to know how soon after exercise I should eat for weight loss……….whether I ate before the workout of not?

  9. Mike Geary

    Hey Jonny, great article! This discussion is always controversial, so I’m glad you found some good evidence for the empty stomach argument.

    I’d also add to the individuality point… if somebody’s goal is simply building muscle, they may not want to do the empty stomach workout, as max strength and force will be greater if some carbohydrates have been ingested. Also, strength testing shows peaks for many people in late afternoon to early evening, which means they wouldn’t be in a fasted state if they worked out at that time.

    So for weight training with strength or mass goals, I think we definitely need some food in us. But for interval training or cardio training, I think there’s something to this empty stomach morning cardio thing…

    I’ve personally tested empty stomach morning cardio over the years, and I found something interesting… if I did the morning cario on an empty stomach (with zero supplementation), I found that I tended to lose lean muscle mass fairly fast over the course of 2-3 weeks. This is NOT good as it will reduce resting metabolic rate.

    However, when I do morning cardio on an empty stomach but also supplement with about 4-6 grams of BCAA’s (branched chain aminos) first thing upon waking to prevent excess catabolism, I found that I don’t suffer the same lean muscle loss… in fact, my strength levels even increased during my last cycle that I tested this!


  10. Winnie

    Good to know this facts.

  11. Peter Morrison

    The best thing to do, is eat little before excercise, but potent.
    Eggs, yoghurt, etc a little just to be ready..then the best weight loss move ever is “ALWAYS EAT WITHIN 30 MINUTES OF YOU WORKOUT”..tuna fish sammy, soup and salad etc…Dr J can tel you and so can I, that is when you best action on your food intake happens.
    So think little before workout then big good stuff after Within 30 Min
    peace, PMo

  12. Bill

    I’ve experimented with this in the past and noticed that what time of day I work outalso influences how well I feel working out on a fasted stomach.
    If I work out early in the day, before breakfast, I tend to have maximum energy, even though I have an empty stomach. I understand that this is from having enjoyed a night’s rest that has left me energised, with my batteries recharged. As long as I get some food in immediately after exercising, I’m good for the rest of the day.
    On the otherhand, if I go through a full day’s routine, and then head to gym in the evening, having eating 4 hours earlier in order to let my stomach empty, I find I have less endurance. I think this is because my system hasn’t processed the food, or had the chance to rejuvenate through sleep, so it feels tired by day’s end. Not really rocket science is it?
    Natural Hygiene recommends exercising on an empty stomach, or eating no more than a light meal of fruits 30 mins before the workout, which I find also works for me. What you put in after the workout is vital too.

  13. Armando Rocha

    Amazing research Jonny!
    I knew a little bit about exercise on an empty gas tank, but I didn’t know it benefited so much in terms of fat burning.

  14. Tianna

    Dr. Jonny,

    I wish I could exercise regularly, I really do. I’m 23 and I feel like I’m 50. I supplement and try to create the healthiest diet for myself to the point of almost obsession, and yet, I’m sluggish, tired, weak and the condition of my back has my massage therapist and chiropractor disgusted. I’ve got spider veins on my legs worse than my mother from having to sit at work all day. I need to do something with myself.
    I know exercise would help me out, but considering the fact that I have to be up for work at 3:30am and I get home at around 8pm, any exercise regimen would get in the way of my already pathetic amount of sleep. I can barely function as is, so what little exercise I get is confined to every second week on my days off.
    What would be the quickest way of building my body strength and endurance without the xiser, as it’s out of my budget, and without stepping outside? (It’s winter here in Northern Canada and I work at an oil plant in the middle of the boreal forest. I feel it would be a little adverse to my health to stroll around tailings ponds on my breaks.) Is there any point if I can only exercise every second week?

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  16. Tim

    The study noted eating a “carbohydrate rich breakfast” for the non-fasted group – this completely skews everything. ‘Fasting’, OR in this case read as ‘not eating carbs’, did better.

    Here is a link to a Poliquin blog where better results and fat burning was with eating a high protein low carb breakfast instead of empty stomach: http://www.charlespoliquin.com/Blog/tabid/130/EntryId/1963/Tip-566-Eat-A-High-Protein-Breakfast-To-Lose-Fat-Keep-It-Off-Better-Training-Performance-Too.aspx

    The detailed Belgian study also noted specifics like “during caloric overload” and “high fat, high calorie” diets, although I still feel the view of ‘ate carbs’ vs. ‘not eating carbs’ instead of ‘fasted’ or ‘not fasted’ is the more important piece.

  17. Kari

    My first thought on reading this is that 27 people is not a very large number on which to be doing testing. That’s only 9 people per group. I’d be interested to see if they got the same results using 100s of people. And, agreeing with others, it would be interesting to see what the results would be if, instead of eating a horrible diet, the three control groups were eating correctly.

  18. Mary T

    Hi Dr. Bowden,

    I mentioned a while ago that I practice intermittent fasting. I should clarify that I fast daily until 3:00 PM most days. I do not work out like I should but my job requires me to do a lot f moderate lifting and walking. Not only do I do fine, my glucose is within the normal when I get home from work. I work during my fasting hours. I also walk my dogs for about a half hour before breaking my fast. I worked up to intermittent fasting, I did not go wild turkey.

    I also practice a diet that can be mostly described as paleo/low carb/ketogenic. I began “low carbing” when I began Atkins nearly 13 years ago. I added fasting about 6 years ago. I am also menopausal and pre-diabetic.

  19. Mike

    Great article…not sure about the Challenger reference in the fat-burning snacks video…

  20. DJreef

    Sorry, but I never go into battle without ammunition. 🙂


  21. Alan

    Completely wrong.
    Any carbohydrate the body needs, and it’s very little, can be provided via gluconeogenisis.
    I prefer to be in fat burning mode 24/7 and eat little to no carbs and have built a sizeable amount of muscle.

  22. Alan

    My experience seems to be vastly different from the majority here. I always train fasted and often don’t break the fast until the evening. I find exercise blunts hunger anyway. As an experiment, I have fasted for 5 days and trained 90min+ each day with no loss of energy or strength. In fact, lifts even improved. I have been eating and training like this, fully fat adapted, for almost 5 years now and have built considerable muscle. I prefer high fat, moderate protein and little to no carbs baring the occasional green veg and some almonds.

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  24. Abdominal Rejuvenation

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  25. samsperonseo

    Thank you for posting this blog…. Its very useful to control my body weight . Also helpful for follow the good diet

  26. Arvind

    Hi All, I am diabetic. I started working out today and with minimal exercise ( 20 mins of cardio, low intensity, 2 sets of Lat machine, 2 sets of chest press only) I felt faint, giddy, nauseated and felt I would pass out until luckily I ate a small portion of sugar to find my feet back. I would have probably passed out if i had not had that bit of sugar. I was surprising for me as I drank a cup of hot chocolate with just half a tea spoon of sugar before I went for the workout at 6 AM. I guess its quite risky and can even lead to a stroke specially in case of diabetics to workout on an empty stomach early in the morning. Though I guess it depends on person to person. Any thoughts or guidance on this matter is highly appreciated.

  27. Parviz

    Hi everyone.
    Loved this forum and topic . Im an 32 and im in a great shape . I have been working out ffor adacade. On and off so lately. Im going intense . Learning more and more
    From my own experience i can say that , there is no rule single rule for everybody.
    Too many factors to consider to be precise on calling results.
    At least we need to look at factors and combination of them in evr individuals life style. These can be anything from climate to nutrition , food type, portions of protien and carbs , weight of idividual , age , etc… So as i said too many aspects we dont know much about yet . Still to live and learn.
    But i do a fruit or smthng before heavy “iron pump”

  28. Daniel

    Well, I cannot train when my stomach is empty. That is why I usually eat one hour before going to the gym.

  29. Keon Fernando

    Nice Blog!! It contains lot of meaningful information how to reduce body weight. Thanks for sharing.

  30. AK

    Arvind, you had sudden spike in energy due to sugar or any high carb/sugar food. This happens to non-diabetic folks as well. Try the exercise again on an empty stomach (but keep an energy bar with you just in case). If you feel the same, you need a pre-workout meal.
    Also, avoid doing cardio and weight training at the same time.

  31. Dawn

    Nice article. Can you tell us how long after the workout that the relevant group ate? I have read that for muscle recovery and repair, we should eat within 30-45 minutes of a workout. What do you think? Is this time interval also effective for riding on the fat burning wave? Further, for fat loss, is morning or evening workout better?

  32. Neil H. Jones

    I have to completely agree.


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