It really is calories in vs calories out and it's much easier to restrain yourself from having an 900 calorie burger and instead have 300 gr of chicken breast which would fill you just as much, probably more, than it is to do 1 hour of Insanity.
Having said that, Insanity is good for cardiovascular health, just like P90x, Crossfit and they do build a little muscle at the beginning which helps increase your Basal Metabolic Rate since muscle burns more calories than fat. However if that is what you want to do there is no more effective way to do it than lifting heavy weights.
I know a lot of people really don't like weights, but that is the solution to build muscle, all other programs are just trying to reinvent the wheel, ineffectively or in most cases inefficiently.
So bottom line is just want to lose weight eat less. Want to eat the same, then excersice. You are hungrier when you workout, build muscle, raise your BMR. Want better health, do some type of cardio, I'd recommend Crossfit as it involves a little weight and some functional movements. It is 80% diet 20& excersice, in order of importance, ideally one would diet (eat right), lift weights and do cardio.
