Exercising on an Empty Stomach and Fat Loss

Young woman sitting in the gym with a bottle of juice and other person behind her
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This is a popular theory based on the idea that your blood sugar levels are low when you've gone all night without eating which, supposedly, targets more fat burning during exercise. But does working out when you're hungry help you burn more fat?

Not necessarily. The problem is that just because you're using more fat as fuel doesn't mean you're actually burning more fat off your body. Burning fat is more about overall calorie expenditure, not just about the type of energy your body is using for your workout.

Fasted Workouts

At least one study, published in the National Strength and Conditioning Journal, has shown that your calorie burn is the same during cardio whether you eat or not. In fact, the study's author Brad Schoenfeld suggests that working out in a fasted state may affect your protein stores, reducing it by up to 10.4%. If you're trying to build muscle, that's a big loss.

As he says: "As a general rule, if you burn more carbohydrate during a workout, you inevitably burn more fat in the post-exercise period and vice versa."

Finally, if you skip your meal or snack, you may not be able to work out as long or as hard if you're hungry. That means you may end up burning fewer calories than if you'd eaten something and worked harder.

Benefits of Eating Before Exercise

We each have to find a system that works for us. You may be fine doing cardio without a meal in the morning, but strength training may require more fuel to really challenge your muscles. Here are some of the benefits to eating before working out:

  • Avoid low blood sugar, which can make you feel dizzy or nauseous
  • Boost recovery and strength gains
  • Make your workouts more enjoyable (since you're not thinking about eating the whole time)
  • Sustain longer, more intense workouts

The best answer is to do what works for you. Don't go hungry just because you think you're burning more fat. After all, if you cut it short or lower the intensity because of low energy, how much fat are you burning anyway? The thing is, you may need to experiment before you find what works and what doesn't.

If you do eat before a workout, make sure you give your body time to digest. The larger the meal, the more time you'll need. But, if you choose a light pre-workout snack (100 to 200 calories) and stick with higher carb fare, you can probably exercise after about 30 to 60 minutes.

Pre-Workout Snack Ideas

  • Apple with cheese
  • Banana or any other type of fruit
  • Energy bar or gel
  • Fruit smoothie
  • Greek yogurt with fruit
  • Oatmeal
  • Sports drink

If you just can't stomach eating anything early, just try a sip of orange juice or maybe a couple of bites of a granola bar. Even just a little energy can make a difference in your workouts.

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Article Sources
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  1. Schoenfeld, Brad MS, CSCS. Does Cardio After an Overnight Fast Maximize Fat Loss?. Strength & Conditioning Journal 33.1 (2011): 23-25. doi:10.1519/SSC.0b013e31820396ec

  2. Ormsbee MJ, Bach CW, Baur DA. Pre-exercise nutrition: the role of macronutrients, modified starches and supplements on metabolism and endurance performance. Nutrients. 2014;6(5):1782-808. doi:10.1093/jn/nxz018