NBC's Ed is about to turn viewers into weight watchers. In September, Michael Genadry, who plays heavyweight high schooler Mark Vanacore, underwent gastric bypass surgery, and already he's dropped 70 pounds. Now, on Tuesday's episode (airing 8 pm/ET), the 24-year-old's character will submit to the procedure, which essentially reduces the size of one's stomach. "I started off over 450, and now I'm under 400," Genadry says proudly. "I don't see a difference, but everyone around me does."

Count exec producers Jon Beckerman and Rob Burnette among that number. So amazed were they by Genadry's transformation that they felt obliged to incorporate it into Mark's story. "We didn't want to mislead the audience [into thinking] that it would be possible for somebody like Michael to lose such a large amount of weight so quickly," explains Beckerman. "If we just portrayed this as if he went on Weight Watchers, we would be misrepresenting what was actually happening."

In order to deliver the most "accurate portrayal of the journey possible," Burnett says he and Beckerman consulted with Genadry's doctors to make sure they got all their facts straight. "But our purpose here is not to sell anyone on the idea of gastric bypass," adds Beckerman, who points out that the "surgery is not without controversy. There are those who argue against it and those who argue for it, and Michael was very open to us representing both viewpoints on the show."

For his part, Genadry hopes the storyline will shatter some of the fears he had about the operation, which has also been responsible for the slimming down of singer Carnie Wilson and Today show weatherman Al Roker. "I've never known any other way to live than being fat," sighs Genadry, who recently became engaged to TV technician Jen Cleary. "So, when you think about this [turning point], you kind of worry that your life is going to be over after that; you won't know what to do with yourself. But there is life after change, which is hopefully what we'll convey."
To go behind the scenes of this special Ed episode, click here.