ChaLean Extreme

If you eat only 1300 calories a day and you burn , let's say 500 during 1-1/2 hrs exercise, that gives you a net calorie count of 800 for the day which is way too low. Your body will start burning muscle tissue as well as fat for energy, because it can only convert a certain amount of fat at a given rate. Plus calorie consumption that low slows your metabolism. Really,1300 is a bit low too depending on your height/overall weight,1500 is more ideal. But yes, eat those calories you burned during your workout; don't think of it as a wasted workout, look at it this way- you can eat 1300 calories and not workout; or get to eat 1800 calories with a 500 calorie workout.
Hopefully this answers your question