Stephanie Soechtig’s food documentary buzzes the message into us with the speed and precision of a cranial saw: Sugar is a poison. Sugars are deadly. They will give you diabetes. They are responsible for the worldwide epidemic of obesity. Sugars are attacking Americans, particularly the young and poor, from all angles, in processed foods and especially soft drinks. And the companies that poison us are rich and powerful and have a vested interest in feeding us lies as well as their deadly products. This doc is strong stuff, with plain talk from such talking heads as Marion Nestle, Michael Pollan, Tom Harkin, Bill Clinton (“We’ve got to change the diet of America”), and other public figures alarmed by the plight of the film’s other subjects, a random-looking group of seriously overweight kids cruising toward ill health (92 min.).