Diet and fitness apps were used by 55.7 million American adults in 2013, up from 43.9 million in 2012, according to a study by Kantar Media's MARS OTC/DTC Study of 20,000 consumers.
The study found that 129 million American adults (55 percent of the population) own either a smartphone or a tablet or both -- 116 million (49 percent of the population) own a smartphone and 64 million (27 percent)...
