I am interested in exercising first thing in the morning when before I eat due to my schedule. I have always heard that this causes damage to your body due to the nature of fasting while sleeping.

Can anyone shed some light on this?


  • 1
    In addition to the correct answer you've received, time-of-day doesn't seem to have any relevance in scientific studies. ncbi.nlm.nih.gov/pubmed/18608836
    – Eric
    Oct 5, 2014 at 21:41

3 Answers 3


The short answer is no. The long answer is maybe.

The basic "model" of the body's energy supply is that it holds a certain amount of sugar (glucose) in the blood if the number gets too high, it binds the blood sugar with insulin and stores it in fat cells. If the number gets too low, the body uses glucagon to un-bind the sugar and return it to usability in the bloodstream.

The body can also store glucose in the liver and muscles by turning it into glycogen, instead. So when you need sugar you don't have you dip into your stores, and when you have too much you store it for later.

This is all a drastic oversimplification, bordering on lies-told-to-children, but it's a good enough model. And it shows that in a normal person it doesn't really matter if you exercise on an empty stomach or not: your body can make energy for you and replenish it later. It's not going to attack itself just because you don't have something in your stomach. If you're trying to build muscle, you'll want to have protein available to build with and the best way to have it available is to eat it before or just after you work out, but that's more adding muscle and less avoiding damage.

Have no worries, your body is smart. It will happily maintain your blood sugar sparing you trying to exactly match eating to your expenditures


Your body isn't that smart. Some people have metabolic illnesses, including but not limited to diabetes, that can alter this process and result in them needing to follow special instructions from their doctor regarding diet and exercise. For these people, it is drastically important to follow this because their body is not doing the same things as everyone else's. If and only if you are in this group does it matter.

tl;dr Unless told otherwise by a doctor, it doesn't matter so workout whenever makes sense for you.


J.T. Hurley's comments about having protein available for muscle growth to occur can absolutely NOT be overstated. If you're intentions for working out are to gain muscle mass and increase your overall strength, you would be doing yourself a tremendous disservice by not having plenty of protein, calories, and water readily available before, during, and after your workout.

If you're thinking of more of an aerobic workout in the morning with more endurance activities to decrease your body fat parentage, then its slightly less important but only for roughly the next six months or so. After this grace period your body will begin to adapt and store more body fat in response to the excess calories that you are now consistently burning. So, inevitably you'll be forced to engage in more intense physical activities such as sprinting and resistance training which will essentially force your body to burn calories in the post-workout period as it repairs and creates new muscle fibers.

No matter what your short term goal is, to continue to see improvements in your physique and/or your over all health then you are going to have to build muscle. And to do that most efficiently will require a steady supply of nutrients before, during, and after your workout. Unless its completely impossible, I would seriously consider altering your schedule so that you can consume some form of nutrients and plenty of water at least 15-30 minutes before your workout for optimal gains, and to reduce any chances of hypoglycemia or dehydration from occurring.

Which to answer your question directly would be your two greatest dangers from a metabolic perspective. Your CNS is not going to be firing on all cylinders, but as long as you do a thorough warm up that shouldn't be a problem, as you'll adapt to being up and exercising that early over time barring any sleep/anxiety disorders.


I agree that working out on an empty stomach will not damage your muscles, but if I may offer my personal experience, working out on an empty stomach is no good....and obviously training when you are stuffed is also no good, unless you want to make yourself vomit. The best thing would be to have a carb rich meal about 2 hours before working out, and then go for it. You would not believe how much of a difference it makes and how much more you will be able to lift. I dont know exactly why though. I reckon it is the period when you are digesting the food and the body is consistently supplied with energy and you are using it immediately, which is more efficient than breaking down stored energy, but I am not sure about the exact mechanism. Another reason to avoid first thing in the morning workouts would be the lack of concentration. Obviously, it depends on how long it takes you to wake up, but being a bit drowsy can really make for a bad workout, and just because you feel awake, it doesnt mean your are awake enough to start for example bench-pressing. You may find that you are less sensitive to this, but if I was to workout first thing in the morning, my workout would be severely suboptimal. But even if this was the same case with you, a morning workout is still better than no workout, so if you have no other options, go for it.

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