U.S. consumers who have had their fill of finding protein added to everything from cereal to ice cream are about to meet the next big food fad: fiber. Americans have been boosting their protein intake for years; even Pop-Tarts and Starbucks are selling protein-enhanced products. But the number of new products promoted with high or added fiber saw a big uptick in the U.S. this year, according to market research team Mintel.