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Fuel To Burn: Why Only Fat-Loss Fools Train On An Empty Stomach

Cardio on an empty stomach has long been touted to burn fat. But the downsides outweigh the benefits.

It's a common practice for athletes, bodybuilders, and other fat loss die-hards to wake up early, skip breakfast, and jump right on the treadmill with an eye toward obliterating body fat. This strategy has been employed by many great fitness athletes, and has received credit for helping them getting rid of those pesky extra pounds.

The common rationale for the fasted morning workout is that low glycogen levels cause the body to use fat rather than carbohydrates for fuel. Unfortunately, this flies in the face of basic exercise science and physiology. Let me explain.

The benefits of food consumption—particularly of glucose and protein—far outweigh any perceived benefits from fasting. Having these substances available as fuel will limit protein loss and thus maintain muscle mass, increase performance, and increase fat oxidation post-exercise. For most of us, these are the goals that cause us to work out in the first place.

The Fuel Continuum

Normally, the body will use all fuel sources—including carbohydrates, protein, and fat—during exercise. Depending on the intensity and duration of exercise, one will become the primary fuel, but only for a limited time.

When using carbohydrates as the fuel source for a workout, the body will shift toward greater usage of fat post-workout. Alternatively, if the body burns fat during cardio, it will use carbohydrates afterward. High intensity levels of training, such as HIIT training, produce a greater dependence on carbohydrates as fuel during workout. Then, following this workout, those who follow HIIT will continue to burn fat for far longer than they were in the gym.

It's important to remember that this fuel delivery system operates on a continuum—it's not simply one fuel source or the other. Many factors determine which fuel source the body will tap at any given time, and it is better to think of fat-burning goals in a time frame of days rather than minutes. In other words, the fat loss from any one early-morning cardio session isn't going to have a significant effect on body composition or overall fat loss.

The Fat-Burning Myth

So basic physiology casts doubt on the effectiveness of the fasted workout. What's more, specific research hasn't been much more supportive.

In one study at the University of Texas at Austin, moderately trained individuals were divided into two groups. One fasted prior to performing low-intensity cardio, and the other consumed carbohydrates. There was no difference between the groups in the amount of fat oxidation during the exercise until the 80-90-minute mark of exercise, at which point there was slight increase in fat oxidation for the fasted group. In the same study, moderate-intensity cardio produced no difference between the fasted and fed groups.

Two other studies took the same idea and applied it to endurance athletes. Again, no differences were found between fasted and fed groups. The fasted groups in these studies showed evidence of fat being liberated from adipose tissue, but that fat was never fully oxidized. This means that it was re-established into fatty tissue on the body after the exercise bout. So the technique failed the primary goal of early-morning fasted cardio.

Eat Up And Still Burn

From an exercise perspective, there are multiple reasons to eat before working out. First and foremost, attempting to engage in high-intensity training on an empty stomach will undermine your performance. Having a pre-training meal primes the body for performance and provides the fuel needed to satisfy the demands of the session. Training intensely on an empty stomach will demand caloric expenditure that the body cannot fully meet, leading to diminished returns.

Another benefit of eating before exercise is the thermogenic effect from the digestion of the food, which multiple studies have shown actually improves fat oxidation. The process of digestion causes the body's temperature to rise, leading to a greater use of nutrients during exercise. The high level of oxygen consumption during intense exercise intensifies this effect. Indeed, it has been shown that greater use of both fat and carbohydrates occurs after consuming glucose before low- and high-intensity training when compared to not consuming glucose before exercise.

If your goal is muscle growth or maintenance, fueling up is doubly important. Going into cardiovascular training hungry puts you at risk of significant loss of protein. When each gram you consume is valuable, fasting isn't your fat-loss friend.

The Numbers Game

So what's to explain the success many claim with fasted early-morning workouts? Well, the person is working out, and this burns more calories. The same would hold true if you went from training once per day to twice per day, or if you changed from a sedentary lifestyle to regular exercise. As the caloric demand on your body increases, chances are you'll lose weight.

That's a positive development—but training in a fasted state sets you up to lose the muscle you have worked so hard to create. Eat before you leave for the gym for a better workout experience and better results. And did we say you get to eat breakfast?

Sources

  1. Febbraio MA, Chiu A, Angus DJ, Arkinstall MJ, and Hawley JA. Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance. J Appl Physiol. 2000; 89: 2220-2226.
  2. Gibala MJ, Little JP, van Essen M, Wilkin GP, Burgomaster KA, Safdar A, Raha S, and Tarnopolsky MA. Short-term sprint interval versus traditional endurance training: Similar initial adaptations in human skeletal muscle and exercise performance. J Physiol. 200; 615(pt 3): 901-911.
  3. Horowitz JF, Mora-Rodriguez R, Byerley LO, and Coyle EF. Lipolytic suppression following carbohydrate ingestion limits fat oxidation during exercise. Am J Physiol Endocrinol Metab. 1997; 273: E768-E775.
  4. Horowitz JF, Mora-Rodriguez R, Byerley LO, and Coyle EF. Substrate metabolism when subjects are fed carbohydrate during exercise. Am J Physiol. 1999; 276(5 Pt 1): E828-E835.
  5. Lee YS, Ha MS, and Lee YJ. The effects of various intensities and durations of exercise with and without glucose in milk ingestion on post exercise oxygen consumption. J Sports Med Physical Fitness. 1999; 39: 341-347.
  6. Lemon PW and Mullin JP. Effect of initial muscle glycogen levels on protein catabolism during exercise. J Appl Physiol. 1980; 48: 624-629.
  7. Schoenfeld B. Does cardio after an overnight fast maximize fat loss? Strength and Conditioning Journal. 2011; 33: 23-25.
  8. Schabort EJ, Bosch AN, Weltan SM, and Noakes TD. The effect of a preexercise meal on time to fatigue during prolonged cycling exercise. Med Sci Sports Exerc. 1999; 31: 464-471.
  9. Wright DA, Sherman WM, and Dernbach AR. Carbohydrate feedings before, during, or in combination improve cycling endurance performance. J Appl Physiol. 1991; 71: 1082-1088.

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About The Author

Brad earned his Master's degree in Exercise Physiology and also holds numerous certifications to help people reach their true potential.

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ascc84

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ascc84

if working out early in the morning with an empty stomach is a bad idea then what type of food would you suggest before working out? and how long after the meal should you work out? in order to benefit fat lose and muscle growth

Nov 6, 2012 6:26pm | report
 
AngelFaust

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AngelFaust

sorry but this is bull, ive been intermittent fasting and training on empty for a while now and my gains both in terms of muscle growth and fastloss have been throught the roof, these studies dnt account for hormonal effects of the adrenals and HGH

Nov 6, 2012 6:33pm | report
 
Hyaline

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Hyaline

agree, man. Who do you think pays these "scientists" to do all this research and publish it? I've been IF-ing for 2.5 months now and seeing gains in muscle and loss in fat.

Nov 6, 2012 7:14pm | report
TheBartBarton

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TheBartBarton

Yeah Brad, your philosophy doesn't work for me at all. IF-ing helped me lose 25 lbs of fat over 3 mos. If i need to step it up, I'll fast for 1-3 days. And burn much more fat. The research I read says the body will burn its fatty acids for three days for energy and not burn muscle until the fourth. My results agree with that. Perhaps you're actually the fool?

Nov 6, 2012 8:22pm | report
matsanity

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matsanity

I agree as well.. Intermittent fasting has given me great results!

Nov 7, 2012 1:46am | report
KennyK

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KennyK

i agree. IF is the truth

Nov 7, 2012 9:06am | report
RPullen

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RPullen

It's important to note that you body can go into retention mode if you starve it, leaving you with less energy and a slower metamobolism. What is good to know also is that light foods like fruit and some carbs can give you the boost to push further and burn the carbs/fat even quicker.

Nov 7, 2012 10:39am | report
kiestonreece

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kiestonreece

It's not "bull", as you put it. If it doesn't work for you; fine. Fitness is different for each individual. I train in the morning and NEVER on an empty stomach. Do what works for you; but dismissing it as "bull" is BULL

Nov 7, 2012 11:12am | report
Achezallover

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Achezallover

kiestonreece, this article is presented as objective physiological truth, not something "different for each individual". It goes so far as to call IF'ers "fools", so if you're criticizing a dogmatic approach to the topic, your guns are pointing the wrong way.

Nov 7, 2012 12:58pm | report
kiestonreece

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kiestonreece

I respect that. Overlooked the "fool" portion.

Nov 8, 2012 8:23am | report
DatNativ21

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DatNativ21

agree ive been on IF for 2 weeks been losin all kindzzzz of fat and makin alll kindz of gainzzzzz

Jan 24, 2013 9:42pm | report
Pirolai

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Pirolai

A lot of great advice! Thanks guys. But I just started a IF diet as well. It is called the "Renegade Diet" by Jason Ferruggia. He explains how to do his diet plan and gives reasons why...

Mar 11, 2013 9:25am | report
dtcummings

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dtcummings

co-sign... IF is the truth.

May 31, 2013 12:20pm | report
Burrex

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Burrex

I agree.

Aug 14, 2013 12:15am | report
alexcuba1

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alexcuba1

I agree, I have been on IF for a year now and my gains are better then ever and the fat has just melted away. I did the 6 meals a day and it just didn't give me what IF has!

Aug 25, 2013 2:16pm | report
cottage7

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cottage7

According to new studies, it take approx 48-72 hours before the muscle turns into fuel. Gained muscle and lost fat way more in my diet by lengthening my eating windows with far greater convenience.

Sep 23, 2013 11:04am | report
dylanbohn95

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dylanbohn95

IF is the only protocol that gave me the results iv been striving for. I don't think I was in a big enough caloric deficient because I only wanted to lose like 5 pounds so I tried to not loose that much weight a week. This was a nooby mistake I don't intend to make again.

Nov 14, 2013 8:43am | report
dumbjock25

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dumbjock25

as a researcher of a major university, the info that he says is actually true. As for the increased HGH levels associated with IF, human growth hormone actually does not have an effect on muscle growth. And for everyone who is going to argue that point, go on google scholar and type in HGH supplementation, or HGH and muscle hypertrophy.

Nov 21, 2013 9:08am | report
siddiq69

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siddiq69

HGH sure doesn't affect muscle growth but it gets the fat melting off like butter, insulin on the other hand retains fat. I haven't seen or heard of a single person who didn't make real good fat loss and muscle gains with IF.

Dec 9, 2013 4:39am | report
bdd549

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bdd549

I never have enough energy to workout if I don't eat at least an apple.

Nov 6, 2012 7:11pm | report
 
tclaxer23

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tclaxer23

I too normally train on an empty stomach. My fat has greatly decreased and my muscle/strength growth is constant. Although you said taking carbs pre, your body will use carbs to use during a fat post. what if i dont eat and take a protein shake such as hydrobuilder with a scoop of glycomaize? that there does the replacing of the carbs postworkout would it not?

Nov 6, 2012 7:16pm | report
 
Jandonian

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Jandonian

What about if you take amino acids on an empty stomach to preserve muscle mass? I've been doing this with seemingly great results. First thing in the morning i mix my amino's, do cardio (moderate to high intensity depending on my goals) and eat immediately after a proper breakfast. Weights at night.

Nov 6, 2012 7:21pm | report
 
Kaynott502

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Kaynott502

I'm with you, I've been taking 10 grams of BCAAs pre workout after a twelve hour fast. I'm lifting first and running a 5k post workout 3 days per week and HIIT alone one day. The weight is coming off so fast you can almost watch it. I think maybe this guys extrapolation has a place somewhere but not in my playbook. Fasted training is my miracle worker.

Nov 7, 2012 6:03am | report
Urien

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Urien

Hi!,

Interesting article!... Just wanted to know, instead of eating something, would it be better if I take a BCAA shake with zero calories? I think that should replenish the glycogen so there will be no muscle loss while burning fat right?

Nov 6, 2012 7:41pm | report
 
Daftpulse

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Daftpulse

This article was a good laugh.
My IF transformation says otherwise :)

Nov 6, 2012 7:48pm | report
 
Showing 1 - 25 of 85 Comments

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