I usually don’t butt into other people’s conversations with whom I am not acquainted, especially when it comes to training.  Mainly because disagreeing with their “broscience” causes battle lines to be drawn and the outcome is always the same.  They leave thinking you are a jackass and you leave frustrated.

This morning, however, I overheard one of the members trying to convince another one that the best way to burn fat is to do cardio in the morning on an empty stomach. 

Usually, at risk of sounding like a cocky know-it-all I avoid conversations like this with people I don’t know but she continued on to say that she never eats breakfast in the morning and does 45min of cardio before bootcamp class.  This is right about where you hear the breaks screech and me throw it in reverse, almost like a cartoon.

I politely added in “Are you sure thats the best way to burn fat?”.

She very non chalantly replied “One of my friends told me…….”

All I heard after that was blah, blah, body burns fat on empty stomach, blah blah, carbohydrates get used first, blah, blah.  Keep in mind that it is still pre-6:00a.m. and I have heard it all before.  I was listening on autopilot with my finger on the trigger ready to drop the knowledge bombs.

Fastforward to the end of the conversation you would have heard something along these lines:

“Steve, your my hero”

“All in a day’s work ma’am.”

I can’t blame her for spreading this nonsense since it is a very common myth and people will do anything to burn fat.  This one was actually popularized by Bill Phillips in his book, “Body for Life”.  He proposed that by doing 20min of cardio in a fasted state burned more fat than after consuming some chow.  His rationale was that low glycogen levels cause your body to shift energy utilization away from carbohydrates, thereby allowing greater mobilization of stored fat for fuel.

Here is the bullet point of some of the things I explained:

  • It is shortsighted to look solely at how much fat is burned during an exercise session since the human body is very dynamic and continually adjusts its use of fat for fuel.
  • Fat mobilization is governed by many factors such as hormonal secretions, enzyme activity, transcription factors, stress levels, overall activity levels, etc.  Therefore fat burning must be looked at over the course of days, not hours.
  • If you burn more carbohydrate during your workout, you will inevitably burn more fat post-workout and vice versa.
  • High intensity interval (HIIT) has been proven to be a superior method for burning fat compared to steady state training.  Although you don’t burn more fat during exercise, you burn more over time which provides evidence that 24-hour energy balance is more important when trying to reduce body fat.
  • Recent studies show that during moderate-to-high intensity cardiovascular exercise in a fasted state by untrained individuals more fat is broken down than the body can use for fuel.  Free fatty acids that are not broken down become re-esterfied in adipose tissue, nullifying any lipolytic benefits afforded by pre-exercise fasting.  Febbraio et al.
  • Various studies have proven that consumption of food before exercise increasses the thermic effect of exercise.  A study by Lee et al. proved that consumption of a glucose/milk beverage increased EPOC much higher than when in a fasted state. 
  • Fasting affects your energy levels and ultimately will lower the intensity of exercise you can maintain.  Studies have proven that a pre-exercise meal allows you to exercise more intensely and for longer and will result in a greater number of calories burned both during and after physical activity

Ha, broscience is no match for my actual science!

Anyways, the moral of the story is that there is no evidence that points towards pre-exercise fasting as a method of burning more fat.  There is a chance you may burn as much fat as after eating a breakfast but research has proven that you will achieve inferior results. 

Not to mention the fact that exercsing in a fasted state will affect muscle strength and hypertrophy negatively.  And if your main goal is becoming strong, lean and sexy as hell you may want to consider building lean muscle as your primary method.  Just sayin’.


Written by Steve