If you ask Coach Jenny from runnersworld.com about running on an empty stomach, she says, essentially, see what works best for you.
What if it works for you on one day, but not on others?
Lately I’ve been experimenting with fasting on Sundays until dinnertime. Given that I tend to let myself overdo it a bit on Saturdays, giving my body a break from eating until Sunday dinner feels surprisingly calming and peaceful.
On two of the three Sundays I’ve tried this, I just went out for an easy 4-mile run around the neighborhood around midday with no issues. I ran with the same state of mind as the fasting: nice and chill.
On the other Sunday, I was coming off a frustrating three-day period in which I hadn’t worked out at all, so I really wanted to get after it, and I did: 3 miles ladder workout on the treadmill, followed by 6 miles as hard as I could go on a stationary bike.
Again, no issues whatsoever from lack of fuel.
So why is it that on other days I invariably feel like I can’t possibly head out without a pre-run snack?
My theory is that it’s all about mindset. On the days I’ve tried this, I’m very focused and purposeful. Does that mean I’m in “monkey mind” every other day of the week? Maybe so. All too often I head out for a run hoping it will calm me down and wipe away the stress of the day. I’ve never really thought about getting in a calm state of mind BEFORE the run until this experiment.
I don’t plan to make it a habit to forego my pre-run snack. I love to eat too much to do that! Still, there is something interesting going on here that bears more investigation…
90in9 
I run into this every now and again myself. I never eat anything before my 6 pm Tuesday rides, I eat after. Sometimes though, when I get home I’m very hungry. I know that if I try to perform at a high level without a snack, I will be sunk, so I’ll have a banana or energy bar. If I’m just going out for an easy ride it’s not so necessary but if I’m going to be riding hard, I have to make sure I’m well fueled.
Great post.
Seems like I’m always looking for an excuse to eat and a workout always seems like a great excuse. But clearly it’s not always necessary. It’s hard work but interesting (and incredibly rewarding) trying to outwit my natural impulses. Thanks for adding your perspective to this, that’s good to know.