Interval training (speedwork) does burn extra calories, but nothing like what is being promised. Plus trying to do that workout six days a week every week will result in burning yourself out.
A good rule of thumb is to mix one or two speedwork days into your training regime, and also throw a longer distance day in as well. The changing of paces (faster for shorter distance and slower for longer distance) will work different muscle groups. Additionally, the longer distance runs will raise the metabolism and continue to burn calories long after you have finished the workout. Most importantly though is that you should listen to what your body is telling you, and know when and if you are pushing too hard, or not pushing hard enough.
I would recommend runnersworld.com as a good resource for training advice, as they have world-class athletes and trainers on staff to make sure the information they share is very accurate.