Morgan Spurlock assigned himself a 30-day diet consisting exclusively of McDonald’s food, monitored his health with a slew of doctors, and videotaped the whole process. The results are predictably horrific, superficially entertaining, and as ugly as the obese individuals the camera can’t seem to get enough of whenever it strays from the relatively slim hero and his girlfriend (a vegetarian chef). Spurlock’s smirking heavy-handedness appears to be inspired by Michael Moore; he even accompanies a diabetic’s stomach surgery with the Blue Danube waltz. Insofar as one can distinguish the investigative research from the career move, this Sundance prizewinner is effective muckraking, but as with junk food, two hours after you’ve seen it you’re hungry again, even though your brain has gotten fatter. 96 min. (JR)