I think it's best not to exercise on an empty stomach as your body will burn muscle instead of fat. I found this article that explains it:
I have heard it way too often lately…."My trainer (or someone else) told me not to eat before I exercise in the morning because I will burn more fat if I exercise on an empty stomach." This is simply not true! In fact, the opposite is true. You should eat before you work out to lose weight.
When you wake up from overnight, your glycogen stores (carb stores) are pretty low. It seems logical that since your glycogen is low that you should then use fat for energy if you go and work out. If only it were that easy we would not have the epidemic of obesity that we have! Instead of your body using stored fat to fuel your workout, your body decides to use muscle instead of fat. It wants to hang on to fat, just like you like to hang on to your savings account. Your body treats your fat stores like savings and does not like to have to use them.
In addition, whenever you put your body into significant low energy, it thinks it is starving and that just teaches the body to go into survival mode and hang on to fat. Not only will you store fat, but you also won’t get a good workout. If you have ever hit the wall or felt really low on energy during a workout, it is very likely due to improper fueling before you worked out.
If you are exercising first thing in the morning, I don’t expect you to eat a large amount. Just a small pre-workout snack is enough to tell the body that it has some fuel coming in. As long as the body knows that you are giving it some fuel to work with, it will respond with burning small amounts of body fat. However, it is when the deficit is large (no food after overnight fast) that it will conserve fat storage. Even eating 100-200 calories will do the trick.
If you are not exercising in the morning, but rather at lunchtime or after work, have a small snack before your workout if it has been more than 3 hours since your last meal or snack. Again, a 100-200 calorie snack should be plenty to get you through that workout. Follow the workout with your next meal within an hour or with a snack if it will be longer than that until the next meal.
You will actually lose more body fat and perform better if you eat before working out. If you are still skeptical, give it a try for a few weeks and let me know how it goes!
Definitely dont work out on an empty stomach!! You need fuel to work out full stop. You wont be burning fat you'll be burning muscle by doing that because muscle is the quickest type of fuel the body can access. and to top it all off, because muscle is denser, even if you do loose a bit of weight in muscle form, it wont wont weigh nearly as much as it would if you'd burnt fat off.
Best thing to do is eat 2hrs before, or sometimes if its in the morning i'll get up eat a banana and then wait an hr, you definitely need some kind of fuel!
I usually exercise in the afternoon or evening. If I walk the dogs it is usually before my tea, but if I do a workout dvd or something on the Wii it's usually well into the evening-so I've got the living room to myself and don't have to exercise in front of anyone!!
When I swim it's a lunch time swim and I always make sure I have something before I go-some fruit or cereal bar.
I personally wouldn't exercise on an empty stomach. For all the reasons posted above!!