how about applying the following logic: when would you eat a mammoth? - before or after you hunt it down?

A long time ago my trainer thought I should eat before my workouts. I had always done my workouts fasted just because I work out first thing in the morning. We tried everything, real food, bars, shakes, whatever. All of it made me want to puke. He eventually agreed with me that it just wasn't working.

I lost a lot of weight and gained some wonderful muscle, I think some of that success can be attributed to working out fasted all the time.

The most important thing is to do what works for you.

You really should read about it at leangains.com - there's tons of info there.

Your muscles will not fall off if you exercise fasted. :)

The answer depends largely on:

1. the type of exercise youre talking about and

2. the amount of food you ate before that (perhaps the prior night's dinner)

If you are going to engage in largely glycolytic activity like metcony crossfit stuff i would say that you might feel you hit the wall without some food in your body pre workout. Carbohydrate might be the fuel you need if you feel you hit the wall.

If you are going to engage in largely strength-related resistance training with low repetitions like squats, deadlifts, etc then going in fasted might suit you just fine. (jsyk, even with this type of exercise, i personally have some eggs or meat two hours pre workout)

I have seen many people fit those two broad generalizations. Exceptions exist of course. And like i mentioned it also largely depends on what that last meal was. With all this talk of IFing (which I believe is great, dont get me wrong) you never hear the last meal spoken of. This i believe wholly changes the fasted state.

For example (i dont know your weight of course but): thursday night around 9pm you have a big dinner: maybe 12 ounces or 16 ounces of steak, good green salad, bunch of starch from some kind of potato. Sleep. Wake up Friday morning, go about your business and hit the gym at maybe noon. FIne to go fasted i would say.

But if either you hit the gym a lot later than that, or your dinner on thursday night wasnt all that big obviously your body is going to send hunger signals earlier, and thus might affect your performance.

To sum up, I might say either:

1. if you dont want to overthink the whole matter and youre not seriously lifting big weights (you'd know what i mean if you were) then go in fasted. Chances are you'll be fine, and if not you'll know for the future. Pluses, you'll almost def burn a good chunk of fat if you hit it fasted. Assuming thats your goal.

2. If you do wanna try eating something, i would say to be on the non-vomit side of things, eat small and let it be two hours pre workout.

"Am I doing damage to my muscles by not eating prior to exercise?"

Absolutely not! Both Brad Pilon (Eat Stop Eat) and Martin Berkhan (Leangains) have mountains of data showing no muscle loss even after fasts of 72 hours. Martin suggests, and I agree, that some BCAA before is advantageous tho. I always train fasted and sometimes don't eat for another 5 hours or so, sometimes sooner. Do what works for you and learn to trust your body.

Are you doing damage to your muscles by not eating prior to exercise? I'd say probably not. Whether or not it is optimal for your purposes is a separate question but one I don't feel I can answer.