If you are not insulin resistant (Normal) and trying to lose body fat, you should not eat for about an hour before exercising, allowing for even the slightest insulin elevation to plateau and you can expect great results (see graph above).
On the other hand, if you are insulin resistant (Obese or Type 2 Diabetic), you need to extend the period between a meal and your exercise session to 1-3 hours depending on the severity of your condition. But be careful, because although too short a gap can prevent you from utilizing fat as your primary fuel source, too long a gap poses a risk of hypoglycemia and low energy which could stop you from continuing and confound your workout plan.
