Working out on an Empty Stomach: Is Time-Restricted Eating Beneficial?

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working out on an empty stomachWhen it comes to getting the full benefits of exercise, and particularly burning fat, a question that repeatedly comes up is whether or not working out on an empty stomach is worthwhile. Ultimately, the answer depends on your goals.

Athletes, for the most part, enjoy working out on an empty stomach at least an hour or two before hitting the weights, the track, or the training field. When you’re exercising at a vigorous pace, your muscles draw upon the sugar that is readily available and use it as energy. So, if you’re working out on an empty stomach, your muscles rely on stored glycogen or reservoirs of fat.

Are There Benefits to Working out on an Empty Stomach?

Now, you may have read that last sentence and noted that working out on an empty stomach taps into fat stores, which might make it seem like it’s the clear choice for a fat-incinerating workout. But, hold that thought for a second.

First off, using fat stores as energy is rather inefficient. And secondly, relying on fat to perform vigorous exercise is counter-productive, as you’ll be weaker.

Research studies have shown that fat is more beneficial as an energy source during moderate-intensity exercise. So, if your goal is to get bigger and stronger, or to exercise intensely (e.g., running, cycling, etc.), it’s advised you eat a meal one or two hours prior.

On the other hand, new research is echoing some old-school bodybuilding advice that doing moderate exercise in a fasted state, like steady-state cardio on a treadmill at a walking pace, may enhance fat-burning compared to having food in the stomach.

Research Findings on Meal-Timing

Over the last few years, researchers decided to look at how fat cells behave during moderate exercise in both fasted and satiated states. Recently published in the American Journal of Physiology-Endocrinology and Metabolism, their study findings showed that fat cells are very active, constantly manufacturing and excreting substances that may hold a fair degree of influence over several bodily systems and organs.

The research team looked at 10 overweight and sedentary, but otherwise healthy young men who represented the general lifestyle of most Americans, and observed how meal timing influenced fat cell metabolism and fat-burning. Each had their fitness levels and resting metabolic rate measured prior to testing, including the analysis of fat tissue and blood samples.

On two separate occasions, they were asked to walk at a moderate pace on a treadmill for an hour. One walk was done in the morning in a fasted state, while the other took place a couple of hours after eating a 600-calorie breakfast. The walks took place on different days.

Should You Eat Before or After a Workout?

The researchers analyzed the blood and fat cells after each walk and noticed a significant difference in how the subjects’ bodies metabolized fat. When the participants skipped breakfast, they burned more fat and had lower blood sugar. The activated genes in a fasted state showed a link to better insulin levels, blood sugar control, and metabolic health. On the other hand, when the participants ate breakfast, the total number of calories burned during exercise was greater.

At the end of the day, if you’re willing to wake up and do fasted, moderate-intensity cardio, it may have metabolic benefits. But, if you can’t and prefer eating before exercise, that’s fine, too. As important as meal timing is to athletes and intense exercise, the majority of the population can do what works best for them.

Just remember, if you’re doing vigorous exercise, eating a meal beforehand is highly recommended. The impacts on fat metabolism in a fasted state are best when you are doing moderate exercise and activity. Talk to your personal trainer or doctor if you have an existing health condition, like diabetes, or if you want a program more tailored to your individual needs.

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Reynolds, G., “The Best Thing to Eat Before a Workout? Maybe Nothing at All,” The New York Times, April 26, 2017;, last accessed May 1, 2017.
Chen, Y. C., et al., “FEEDING INFLUENCES ADIPOSE TISSUE RESPONSES TO EXERCISE IN OVERWEIGHT MEN,” American Journal of Physiology, Endocrinology and Metabolism, March 14, 2017. doi:10.1152/ajpendo.00006.2017.