I think it all boils down to DNA.  Some work outs are going to be more beneficial for some people and less for others.  Results don't lie though.  i made it 80 days into the program, lost a minute off my 2 mile time with out running once, lost 7% body fat and 17 lbs.  It may not work for everyone, but it was the first work out that I saw tangible results with.