You may be experiencing a drop in your blood sugar do to the depletion of glycogen during your workout. If you are sticking to a low-carb diet your stores are already at a minimum before your workout so it would be logical that they would be lower after your workout. What I do to combat this is I have a 20gram protein shake 45 min before my workouts and another one immediately after. I also would recommend(if it is possible) working out first and then eating, that way you will take care of your hunger without having to snack My routine is to have my protein shake at work just before leaving and then working out when I get home and then eating about an hour after I finish my workout. Doing this I have been able to keep my hunger pains at bay.