Three new studies, conducted by researchers in Boston and elsewhere, show how much sugar-sweetened beverages can expand our waistlines and provide strong evidence in favor of government policies to curb consumption of soft drinks and fruit juices in schools. David Ludwig, HMS professor of pediatrics at Boston Children’s Hospital, coauthored a clinical trial on obese children. Lu Qi, HMS assistant professor of medicine at Brigham and Women’s Hospital, is a coauthor of a study at HSPH.