Many people believe performing cardio first thing in the morning on an empty stomach maximizes fat loss.  Just when I thought this myth might be dying out, telling myself everyone may already know this by now.  Maybe I should write about something else.  I saw it again in a recent issue of a popular magazine.  I won’t mention what magazine or what well-known expert was promoting it.  The bottom line - this fat loss myth is still alive and well and it needs to be dispelled before more innocent people fall prey to this misconception.

The theory here is that if you perform cardiovascular training in a fasted state with depleted glycogen stores you’ll cause the body to burn fat for energy.  While it may sound sensible to some, scientific evidence doesn't support this fat loss myth.

There are many reasons why this belief is misguided.

First, fat loss occurs throughout the course of the day, not just during the workout itself.  To illustrate, High Intensity Interval Training (HIIT) is proven to be a more effective method for fat loss than moderate steady state cardio, or training in the “fat burning zone.”   When comparing HIIT with moderate steady state cardio, the rate of fat burning is less during HIIT workouts, while the ratio of fat burning is greater during steady state cardio.  However, those who perform HIIT continue to burn more fat hours after the workout is over and burn more total fat throughout the day than those who perform moderate steady state cardio in the “fat burning zone.” In addition, even when the body does burn fat at a faster rate, the broken down fats that are not used are converted back to stored fat, negating any fat burning effect achieved in a fasted state.

Second, the Thermic effect of food, based on scientific laws of heat and energy transfer, states that your body uses energy to break down food for energy.  In other words, your body’s metabolism increases during digestion to break down food.  So by eating breakfast you increase your metabolism through the Thermic effect of food, and by exercising after you increase your metabolism and fat burning potential even more through the Thermic effect of exercise.

Third, food as fuel for your body is elementary health, Training first thing in the morning is challenging enough, let alone doing it with no food for fuel.  If you have breakfast, you’ll have more energy to train harder longer.  If you’re able to train harder during your session you’ll burn more fat throughout the rest of the day.

Fourth, if having a strong, lean body is your goal then, in no way is doing cardio (or any kind of exercise) in a catabolic state a good idea.  Scientists found that training in a fasted state resulted in nitrogen and protein loss.  Furthermore, related findings revealed that when subjects were given a carbohydrate mixture before training it did not inhibit fat burning.  These two points taken together demonstrate the carbohydrate sparing effect of protein, and are very important facts for those looking to maximize fat loss, and increase lean muscle.

The bottom line is, make sure you eat breakfast, especially if you work out in the morning because you'll speed your metabolism, have more energy to train harder longer, burn more fat, and preserve your lean muscle tissue in the process, which is just about everyone’s main goal.

NYC Personal Trainer Andrew Schmarje CSCS 

Schoenfeld, B.  (2011).  Does Cardio After an Overnight Fast Maximize Fat Loss?  Strength and Conditioning Journal 33(1), 23-25

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