Long slow distance work the current research says causes stress on the body which elicits cortisol a fat retaining hormone. My question is are you strength training? If you are not you are burning 25% muscle and not just fat which will slow your metabolism.
HIIT is a great add on for running training but not a cure all for anything, it is another training method. Here is a hyperlink to an excellent article on HIIT and how to incorporate it into your training. www.intervaltraining.net/hiit.html
It is called WORK-ing out for a reason.
I said getting fit was simple, I did not say it was easy.
Cardio burns calories, strength work burns fat.
Eat well to lose weight, exercise to get fit
You can not build a six pack using twelve packs
Often when we seek a magic bullet for fitness we end up shooting ourselves in the foot.
"I think calories are little germs in food that all moms are afraid of" Dennis the Menace