Readers ask: Does working out before breakfast burn more fat, muscle, or hurt my workout?

Between you and me, not a week goes by that one of these questions about exercise, breakfast, ‘fat-burning’, ‘metabolism‘, and ‘burning muscle for fuel’ doesn’t come across my desk:

  • Should you work out before breakfast to burn more fat?
  • Should you eat something first to “boost” your metabolism?
  • If you don’t eat anything before you work out, are you in danger of breaking down your muscle as fuel?

You can find fitness programs and gurus promoting each one of these as a ‘must do’ practice to optimize your workouts and ‘burn fat at a premium’.  No wonder we’re confused. These messages hook our desire to find any trick in the book to make the whole fat loss and body shaping thing easier.

The truth is, you don’t need to addle your brain with all of these details. Nor do you need to micromanage each workout in this fashion.

I’m going to see if I can address all 3 of these concerns in one spot.  I thought of creating 3 different posts for you, yet there is a great deal of overlap with these 3 questions and having it all in one place may provide the best clarity.  It’s also made for a lengthier article, but I think you’ll like the way it came together.

Recent workout and breakfast timing questions from readers

To help clarify, here are 2 examples that help bring these questions into focus.  Each of the following questions was asked on Ask Lani Fitness Expert Column at the Dr. McDougall Health & Medical Center.  I’m including my replies to them.

Re:  Eating before you work out to ‘boost’ your metabolism

Hi Lani,

I recently began an exercise program — I joined a local women’s fitness center and started out with 15 mins. on the treadmill followed by 2 times around the circuit of resistance machines. I’ve been going as soon as I get up in the morning, then showering, dressing, and having breakfast when I come home. My trainer at the gym thinks that’s horrible and says I need to eat “a little something — like a banana or a granola bar before I exercise, to get my metabolism started in the morning.” I don’t know what I would feel like eating at 6 am, I’ve never liked to eat as soon as I get up in the morning. Am I really not getting maximum benefit from my workout because I didn’t eat something first?

Thanks for your help!

Lani Muelrath’s Reply:

Hi  Becky,

I’m not sure what ‘get your metabolism started in the morning” really means and what it would have to do with your workouts. It’s one of those phrases that fitness industry folks like to throw around because it sounds like something we all want, of course! I’m sure your trainer has all the best of intentions.

A recent study shows that eating before a workout is correlated with burning more calories overall during the workout as opposed to not eating before the workout because people feel more energetic with more recent caloric intake instead of working out after a long night’s fast. You could experiment with this and see if it helps, though you didn’t make any complaints. This may be related to ‘maximum benefit’ as you state, though you didn’t qualify what that means to you.

You could try some fruit, or wholegrain cereal, or both. If it just doesn’t appeal, don’t force a big breakfast on yourself. Granola bars are just cookies in a rectangular prism package and best left for survival food in a big pinch.

I almost forgot – congratulations on getting GOING with your workouts! This is wonderful news and will make a big difference in your energy, stamina, shape, and physical confidence.

To your success!


Re:  ‘Burning muscle’ instead of fat

Hi Lani,

Was told this morning by the certified trainer at my gym that because Im not eating anything prior to working out I was NOT burning fat but rather burning muscle? He told me if I ate something then my body would recognize there was food in the stomach and “not worry” and burn fat and leave the muscle alone.

I am not a morning eater. If I eat before like 9am I have and do puke it up so I don’t bother. And since I’m trying to only eat when I’m actually hungry, I don’t feel the need to eat when Im not and rarely am I hungry before 10 am.

My understanding, even limited, is that first we burn stored glycogen then fat and as a last resort we burn muscle for full.

So am I burning muscle when I don’t eat prior to a workout?

Here’s my typical workout: 30 mins on the elliptical or 2 miles then use the weight machines, either whole body or what I have time for, so like upper body or lower body, but always abs! And at least 4 times a week I toss in a 20 walk/run after all that. And at least twice a week I’m on the treadmill for an hour and get in about 4 miles (sometimes this is in addition to the elliptical)

In 2 weeks I have not lost any weight on the scale and while the tape measure isn’t really getting smaller my clothes are fitting better and a tad looser.

But…..I don’t want to burn my muscle when I have plenty of fat to burn instead.



Lani Muelrath’s Reply:

Hi Debbie,

First, our bodies are always ‘burning’ a mix of fuels. The less intense the workload, the greater the percentage that comes from fat because it takes longer to get it through the process of delivering energy. Does that mean we should work out at the least intensity? No, because what you are looking for is overall calorie burn which will find a way of tapping your stored fuel resources.

I say this in prelude to addressing your breakfast question because it is relevant.

When you start exercising, your muscles burn a blend of fuels. For shorter bursts of activity, your muscle cells burn ATP which your muscles are constantly synthesize using carbohydrates, fatty acids and protein.

Exercising for longer periods, your muscles start to dip more into fat stores. But as long as glycogen is available – that stored in your muscles, liver, and carbohydrate recently eaten, your muscles prefer it for fuel because it uses oxygen more efficiently. When the other fuels fuels are less available, your muscles also can tap protein from lean muscle for fuel.

If you start exercising before you have eaten anything for hours, your body may indeed go through the stored glycogen more rapidly and invite your body to dip into fat stores.

But this is where trainers can take the wrong turn and take partial information which doesn’t really serve you in the long run.

Let’s go back to what you are looking for if trying to lose fat weight – an overall calorie deficit. If you work out hard on a fast thinking you are ‘burning more fat’  this is irrelevant if you end up eating enough after your workout to compensate for the calories.

As depleted glycogen invites gluconeogenesis, which is conversation of amino acids to glucose, I want to underscore the advice to eat before exercise so that you don’t have to worry about breaking down your muscle for fuel.

If   looking to achieve a calorie deficit, it is far better for your overall calorie deficit to be able to work out with gusto. Exercising on a fast can leave many people running out of steam and mental stamina for the workload sooner rather than later, affecting the overall quality of the workout. For this reason, having something to eat prior to exercise can actually help the overall calorie burn picture – even something light such as fruit. It is not taxing to the digestion and you may find gives you oomph for a harder workout. It also will help to protect your muscle tissue. However, to extrapolate from that that ‘any exercise on an empty stomach is going to break down your muscles for energy’ is an inappropriate reach.

If you feel sick eating breakfast and you have plenty of steam both mentally and physically to get through your workouts, then you don’t need to force down a big pre-workout meal. And unless you are already quite lean and underweight and working out intensely for extended periods of time, such as over an hour, don’t worry about hacking away at muscle tissue. This is all way much more than you need to worry about. At the same time, for reasons already stated, I do recommend something light before you work out in the morning.

Also, working out after an overnight fast does not mean you are going to just burn off stored fat and make a big difference in your body composition. The quality of your workouts and diet overall are what does that.


Between you and me, bottom line?

  • Whenever you can get yourself exercising during the day is the best time
  • To have more mental and physical energy for your morning workouts, have something to eat first.  This will give you a better workout in the long run, resulting in more calorie burn and more muscle challenge.  It doesn’t need to be a big, heavy breakfast.  Even a piece of fruit or toast may be good choices
  • If you absolutely cannot stand the thought of eating anything first thing in the morning, try something light or just don’t worry about it.  If you are working out for 45 minutes or more, reconsider and do some light fueling first.  You may find that you get used to it and enjoy it after all.

Thanks so much for coming by. Please ‘like’ and share this post and if you’re on facebook, please join me now on my facebook page here: facebook.

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Holloszy, J.O., & Coyle, E.F. 1984. Adaptations of skeletal muscle to endurance exercise and their metabolic consequences, Journal of Applied Physiology, 56, 831-838.

Ivy, J.L., Withers, R.T., Van Handel, P.J., Elger, D.H., & Costill, D.L. 1980. Muscle respiratory capacity and fiber type as determinants of the lactate threshold. Journal of Applied Physiology, 48, 523-527.

McArdle, W.D., Katch, F.I., & Katch, V.L. 1996. Exercise physiology: Energy, nutrition, and human performance. Baltimore, Maryland: Williams & Wilkins.

Fits, R. H. (1994). Cellular mechanisms of muscular fatigue. Physiological Reviews, 74 (1), 49-94. Gardiner, P. F. (2000). Neuromuscular aspects of physical activity. Human Kinetics.

Robergs, R.A., & Roberts, S. 1997. Exercise Physiology: Exercise, performance, and clinical applications. St Louis, Missouri: Mosby.

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  1. Wow what a great article Lani. I too get caught up in all these details and it leaves me so confused. I like knowing I can come here and ask for some simple answers.

    I used to try to work out before eating in the morning to ‘burn more fat’ (!!!) but never had the energy to really make it through a workout like I do when I have something light to eat first, as you suggest.

    Great info!


    • Lani

      Jen, thanks so much for leaving your comments. I wasn’t sure if putting all 3 questions together in one place was going to work or not yet to me it sounds like it does – at least for you!

      Glad to help clear the cobwebs!

  2. It all depends on how I ‘feel’ in the morning. There are days (nights) when I’ve gone to bed and thought, hmm, I’m a teensy bit hungry. On those nights, I push it off because I won’t eat past 8 p.m. Quite typically, the next morning, I am hungry. I will begin my program with possibly a Fit Quicky or two, or maybe Primary Back Stretch. However, I can ‘tell’ my muscles want something. I will only have an apple then, as that is enough fibre and carbohydrates to give me exactly what I need to carry on for the rest of my routine.
    That is how I deal with it. I don’t worry about all the ‘right or wrongs’ behind it all. I do what my body says to do. Oh, i will also eat breakfast if I’ve gotten too far into my day before I exercise!

    • Lani

      Grayce, sounds like a great rhythm and that you know exactly how to read your body. Thanks for sharing the details!

  3. I would have to kindly disagree about the not burning muscle in the morning. When you sleep at night you burn at least half of your glycogen stores up. If you do intense activity including cardio and weights for over a period of 30 minutes your body is going to turn to muscle for fuel regardless if you weigh 100lbs or 500lbs. If your body can’t metabolize the fat fast enough then it can’t use it for energy!

    The breakdown of fat to yield ATP is known as lipolysis. Fat is the most abundant energy source available to the muscle, and the predominant energy source used during the aerobic oxidation phase of energy production.

    Although there is a virtually unlimited supply of fatty acids in humans, the rate at which the body can metabolize them is the limiting factor in obtaining ATP. Lipolysis is the primary source for energy production during rest and low level activity. But, its input to the overall muscular energy supply will decrease as the intensity of muscular contraction increases. When lipolysis is unable to meet the increasing energy requirement of exercise (it is too slow to supply enough energy), stored glycogen from both the liver and muscles is used. Once glycogen depletion occurs, exercise intensity will decline. All exercise intensities (including rest or no activity) that can be maintained for 2 minutes or longer utilizes the oxidative system for energy production. Once approximately 10 minutes of continuous exercise has elapsed, glycolysis is no longer significantly involved in energy production and the oxidative energy system supplies almost all cellular energy for the muscles.

    • Lani Muelrath


      Thanks so much for stopping in with your thoughts. Upon reading your comments “kindly disagree about not burning muscle in the morning”, I read through the article to see to what you might be referring because I had also pointed out the need to fuel up before exercise to avoid gluconeogenesis (conversation of amino acids to glucose) .

      At the same time, it was apparent that the language in the article could be clarified to reflect this, which I did. People too often find reasons not to exercise and the fear of losing muscle by exercising can often overshadow the need to just move.

      Thank you for bringing this to my attention – I appreciate the opportunity to clarify article language to benefit the fitness aspirant.

  4. Hi ..i want to gain weight and muscles..the morning workout at 5 am on smpty stomach is good for gaining weight or not ? …tell me what should i eat in morning before my workout to gain weight ..

    • Lani Muelrath

      Working out on empty is a good prescription for LOSING muscle. Always fuel up before and if your workouts are long and strenuous, during. Solid slow burn carbohydrate (oatmeal) with some quick burning (fruit) makes a great breakfast. Nuts and seeds for more calories, fats and proteins if weight is not a problem.

  5. I do not know whether it’s just me or if perhaps everyone else experiencing issues with your blog. It appears like some of the written text within your posts are running off the screen. Can someone else please provide feedback and let me know if this is happening to them as well? This might be a problem with my browser because I’ve had this happen
    previously. Many thanks

  6. Lani Muelrath


    Can you take a screen shot of what you see and send to me, and also tell me what browser and device your are using? I haven’t received this comment before and would like to help you troubleshoot.


  7. This is great. People are saying to exercise first thing in the morning but as someone who likes to build muscle I am glad this is not the best way to go. I like exercising a couple hours after I eat. The ratio of carbs/fat burning was also interesting. I’m always about keep it simple – simple body weight exercises and simple plant-based eating with no gimmicks. Working like a charm!


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