I'm sure this has been asked before, but I can't seem to find much on it (and google has a lot of articles defending both sides) anyways...

What's the "rule-of-thumb" on exercising on an empty stomach?

I know there are some IFers that probably do it all the time, but if your body is already at a deficit from the day before (I'm a calorie counter) can exercising without some "fuel" be detrimental?

On the flip side though, if I'm not hungry and wanting to workout (say, first thing in the morning) it seems counter productive just to eat so I can workout

What do you all think?

If it's cardio I workout on an empty stomach. If I'm lifting I eat first.

I almost exclusively work out in the evenings, so I try to eat about 1.5-2 hours prior. On Saturdays I workout first thing in the morning and don't eat beforehand with no issues.

Well, you don't want to eat on a full stomach, because then it makes your tummy hurt, or at least, while running or doing any cardio like that. If you want to eat first, put off cardio for at least an hour. But if you absolutely want to exercise, go for it right then and there. If there's no definite answer about it, then it probably doesn't matter either way.

There is some evidence that exercising on an empty stomach forces the body to burn fat for energy. If you have food in your stomach it burns that first.

Yeah, this seems to be what most articles say... I was just worried that too much strenuous exercise without having eaten may effect muscle mass, especially if done frequently and when your body is already in quite a bit of a deficit.

Thank you all for your responses!

PT Jillian Michaels gave his opinion about working out on an empty stomach.
I've just found the thread on jillianmichaelsDOTcom website, in the submenu 'Ask Jillian'.

As far as i'm concerned, i'm very hungry few minutes after waking up in the morning and i feel sore if i don't have breakfast.
So i couldn't work out on an empty stomach (neither if i wanted to )

I have worked out on a empty stomach before in the morning and had no problems ; but I was doing cardio. When ever workingout and I feel that rumbling noise ; I will finish my time and end the workout early.

Here is a good article
http://www.rodale.com/eating-exercise. With research behind it.

I usually eat a slice of dry whole grain toast or a banana...and go do my workout; and then come back and have the rest of my breakfast.

Eating the right food help fuel my body which gives me energy to get through the workouts. Especially now that I am lifting heavier weights I need something in my belly before working out.

I'm a morning work-out person. I eat something small when I get up - oatmeal, toast with peanut butter, that sort of thing. It's usually about 1-1.5 hours before I get the kids to school and get to the park or gym. Then I eat a little more after I'm done - banana, greek yogurt, chocolate milk, etc. On the rare instances that I work out later in the day, I don't necessarily need to eat something extra, but in the mornings, it's been 12+ hours since I ate last.

If I'm doing cardio (particularly stationary bike) I try not to eat too soon before. I find that if I have food in me (even a little) I get wicked heartburn. I think its becuase of my tumy being bounced around it just stirs up whatever is in there. But if I'm doing strength stuff, I'll have a small protein something, otherwise I I'll get very tired and wimp out early.

There's pro's and con's to each option, but its probably most important to figure out what works best for you and your body and stick to that.

During the week, I do evening work outs so I would usually have had my meals for the day. For the weekend, it could be divided throughout the day from first thing in the morning to night time. In the morning, I may have eaten but most of the time I wouldn't. I would never exercise on a full stomach. If I have just had a good sized meal, and did a workout almost immediately, I wouldn't feel too good. During the summer when I had more free time I would usually have lunch and wait about 45 minutes to an hour to start a workout. I think it just comes down to what is best for you and how you feel.

I try to exercise in the mornings before I eat. But lately when I get to the twenty minute mark, I have this awful stomach ache and end up getting sick. So now I wait until I have a few glasses of water and a cup of coffee.

I wondered if it was just me!