Exercising on an Empty Stomach

@dasschus ? for the week: do you burn more calories if you have something to eat first? Went on hike but past lunch & was hungry. on same hike after eating picnic bodybugg said I burned more calories. So does fueling up before exer. burn more calories?

This question is a hotly debated topic among the fitness community: do you exercise on an empty stomach or not? The current theory is that when you perform cardiovascular exercise on an empty stomach, you’ll burn more calories from fat than you would if you ate prior to performing the same cardiovascular exercise. The rationalization is that while you’re sleeping, your body uses up all of the reserve energy in your muscles & when you wake, your body has no choice other than to use the body’s fat reserves to create energy.

Let’s evaluate the pros & cons.


  • Exercising on an empty stomach burns a larger percentage of calories from fat (versus carbohydrate) – but it’s really a small percentage
  • Depending on the intensity of exercise performed, your stomach may feel better while empty


  • Exercising when your muscles are depleted may not allow you to exercise at your optimal intensity
  • Exercising when your muscles are depleted may not allow you to exercise as long as you possibly could

There are few rules that are gospel across all people. This rule is no exception. I feel nauseous if I exercise within 2 hours of eating, and what I’ve learned is that my body is very good at maintaining it’s energy stores; I don’t feel my blood sugar drop like many folks do, my body (and brain) performs very well on low carbohydrate diets. I acknowledge that not everyone’s body works the same as mine. [reference blog post You Are What You Eat]

So, to answer the question, a few things may be a factor here:

  1. possibly you had more energy after the picnic & therefore moved more vigorously
  2. perhaps you were perspiring more because the outside temperature rose, which would register a higher calorie burn too
  3. and although it’s possible, perhaps the Thermic Effect of Food  had something to add to the rise in calorie burn

Great Questions! Keep ’em Coming!