Running on Empty

Researchers at the University of Birmingham published a recent study in April that suggests that you skip your pre workout snack or meal and run on empty in order to rid your body of more fat.  They found that cyclists who trained without eating burned significantly greater amounts of fat than their peers who ate. The hypothesis behind the study was that in the absence of muscles preferred energy source, carbohydrates, it turns to an alternate energy reserve, breaking down fat instead.  You lose a higher percentage of body fat when you skip breakfast pre workout. 

What’s the real story?  A closer look at the research shows that it was conducted on a very small sample size of 14 people.  Both groups were young, healthy adults which is safe in exercise research yet atypical of the US population with 68% adults classified as overweight or obese, 25% hypertensive and 10% diabetic. The study divided participants into 2 groups, 7 people each, cycling 3 times per week with a 1 hour rest break, followed by an additional intense cycling session.  One group was allowed to refuel between sessions and the other was directed to fast.  The results did demonstrate that the group who fasted burned a higher percentage of fat than carbohydrates, however they performed worse.    

The bottom line.  While I’d like to see more research done in this area for individuals struggling with weight loss, I can’t advocate it for competitive athletes.  Nor can I recommend it for young people, pregnant women, or individuals with preexisting health conditions (Type 1 diabetes or hypoglycemia).  Athletes who train for extended periods of time (distance runners), in sports that require concentration to be safe (road cycling) or are at risk of drowning (swimming) are also advised to fuel appropriately.  Symptoms of low blood sugar include headache, difficulty thinking clearly, confusion, hunger, irritability and rapid heartbeats to name a few.  Studies show that people who skip meals also have a greater tendency to binge eat at the next opportunity, reaching for convenience foods that are nutrient poor.    

Without adequately fueling, individuals will not get the intensity they require to see performance improvements.  Serious athletes want to maximize each training session and typically have higher lean body mass than their sedentary counterparts. Their bodies have also already adapted, learning to burn a greater percentage of fuel from fat. Many wouldn’t consider running on empty. According to Andrew Greenberg, the director of Obesity and metabolism Laboratory at Tufts University “You may enhance how you burn the fat in muscles, but it doesn’t affect your overall body fat”.  Ron Maughan, a professor of sport, exercise and health sciences at Loughborough University in Britain cautions against too much exercise on an empty stomach as well stating “It might help you get very good at burning fat, but you won’t be very good at whatever exercise it is you’re doing”.

Categories: Sports Nutrition

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3 replies

  1. Oh god, please tell us all the choice isn’t performing well or being lean. While I 100% feel running on empty (though a great song) isn’t an option for extended, as you said, distance activities. Yet I feel people need a bit of caution as some new to racing or training consumer more in the pre, during and post than they burn off. And the other issue is individuality. Some are fine with a shorter workout with no food before and others cannot run on empty, no matter how short the run (or walk even) is. Great post.


    • Thanks for the comment! I agree nutrition recommendations need to be individualized because what works for one person may not work for another.



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