This is what happens to your body when you work out on an empty stomach

Over the last few months, I’ve pushed myself to become someone who works out in the morning. I had to change a lot of my morning habits in order to make this happen – but the one thing I’ve continually sworn by is having breakfast first. Typically, this is something small before my work out – a half of a banana, a handful of nuts, or a hardboiled egg. The few times I’ve ever skipped eating before a workout all together were when I’d occasionally oversleep before a morning workout class, then must rush out the door to make it there on time (forgoing any kind of breakfast in the process). I can remember my stomach grumbling halfway through and feeling starving by the end of the class. 

But recently, I started to read into the potential benefits of working out on an empty stomach, also known as fasted exercise. When you’re working out without having eaten in the last 8-12  hours, your body needs to rely on another source of energy during the workout – which is why working out on an empty stomach has been associated with fat burning benefits, which in turn leads to weight loss. There are some caveats to this – this method is recommended for a light cardio workout (jogging, yoga, using an elliptical, etc.) rather than weight lifting, because this method can end up breaking down muscle rather than fat. 

Armed with this information, I decided to try it out for a week. Here’s what seven days of working out on an empty stomach was like for me.

Day 1

I had a feeling the beginning of this experiment was going to be particularly challenging until I got used to it, so I decided to try a 30-minute cardio dance workout for my first day to get myself motivated. For the first 20 minutes of class, I honestly didn’t notice much of a difference — until we hit the toning section of the workout, which required a lot of plank holding and gave my mind plenty of time to think about how hungry I was. The remainder of the day flew by, but I didn’t notice any major changes.

Day 2

I decided on a 25-minute jog for the second day of my experiment, and spent some time jogging along the track by my apartment. For the duration of the jog itself I felt pretty good, but the walk back home felt like forever. This was a busy day for me, so my breakfast consisted of only a breakfast bar, which backfired. This day was the hardest – I ended up feeling groggy throughout and had a bad headache. 

Day 3

On day three I opted for an easier workout to give my body a bit of a break and chose a 30-minute yoga class for beginners. I felt really accomplished at the end of it, and while I was hungry, I wasn’t as starving as I had been the two days prior. This time I made sure my post-workout breakfast was protein packed – a slice of whole wheat bread with natural peanut butter. My energy was consistent for the remainder of the day and made me excited to see some benefits from this experiment.

Day 4-5 

Since yoga was really working for me, I stuck to different variations of that work out for the next two days of the experiment. I tried a 30-minute vinyasa class as well as a “sun salutation” yoga, both of which helped set the intention for my day. I stayed with my peanut butter and toast breakfast as well, and by day five I was feeling lighter – but decided to wait until the end of the experiment to weigh myself. 

Day 6

I started to get a little bored of yoga, so I tried another cardio dance class. For most of the class, I was feeling great – but toward the end I hit a wall again. As it turns out, this is something that’s common for fasted exercise – when your glycogen levels are completely depleted, it causes a dip in energy. After having breakfast, I felt better, but decided to find a more manageable workout for my final day.

Day 7

I finished off this experiment with a 30-minute Pilates core class, which I found relatively easy and was able to power through until the end. I switched up my breakfast with two eggs and wheat toast instead of peanut butter, but energy wise I still felt maintained throughout my day. 

The best part of this experiment for me was the weight loss element – in just one week I was down 1.5 pounds! However, I do miss being able to do more intense workouts during the week, so moving forward I think a mix of fasted exercise while incorporating 1-2 days of “normal” workouts might be the best thing for me.