Too bad neither of these tapes comes off particularly well, because they both offer information about diet and life-style that could benefit most Americans. Granted, it’s not easy to hold the attention of sedentary overeaters while telling them they have to start jogging and forsake french fries, but both videos overreach in their efforts to entertain while informing. In The Slim Gourmet (Media Home Entertainment, $39.95), McLean Stevenson provides celebrity credibility and a foil for food writer Barbara Gibbons, who wrote the cookbook of the same title. Over the opening credits the only audible sound is of a food processor. Then our hosts engage in dialogue that is about as natural as vinyl slipcovers. The rest of the tape is organized like a cookbook into chapters with recipes for low-fat meals. While the dishes appear eminently edible, the stilted presentation, ham-handed editing and mediocre production values create boredom, not an appetite. In its efforts to appear spontaneous and fun, The Pritikin Promise (Media Home Entertainment, $69.95) errs in the other direction. Actor Lorne Greene emcees for the Pritikin Team, a cloyingly cheery bunch of boosters filled with pseudoreligious zeal. Nathan Pritikin, the inventor-turned-fitness guru, makes a cameo appearance to deliver his promise of a longer, healthier life for those who follow his program. A lot of time is devoted to trivial fun and games—such as a sequence in which the diet experts gleefully clean “bad” foods out of a refrigerator—and this tape’s largely patronizing presentation will turn off most grown-ups. In the end both videos suffer from their naive approach to instructional video, a problem the industry as a whole has yet to solve.