dieting and weight loss that could hurt your efforts. what is fact and what is fiction is dr. mark seigel from the medical a team. >> this is nis we can all use. one of the people you hear is the best way to lose weight is doing cardio? is that true? >> that's fiction. high intensity interval training. you need bursts of heavy workouts resting and then maybe some cardio. you have to mix it up. that's your best way to lose weight. >> kind of like plyometrics. >> exactly. you want to mix-up the isometrics with the running with the elliptical. change it up make sure there's a high intensity part of it. >> what about incorporating weights into it. a lot of people think weight training is good for your joints. >> that is a fact.