The lady who went on the "fast food diet" only ate 1250 cal/day of which 500 came from TB. You could eat pure fat every day and so long as you didn't go over 1250 you'd lose weight too, especially with exercise.
Love me some Taco Bell. The ad shows the girl in a swimsuit for the before picture but not the after. Thats no good.
The funny thing is the commercial says the stuff is good for losing weight because it's low-fat, with fine print at the bottom saying basically "This doesn't mean it's low-calorie". That should be the first and only warning sign you need.
I eat their meatless products only. A bean burrito and a 7layer burrito is the best $3 lunch you can get.
Actually, if you stick with just the Fresco items, it's quite reasonable for fast food. Check out the nutrition values, not bad. (fresco only!)