“Zero carb!” - a ton of artificial sweetener and fats. Makes up for the carbs twice over with fat, leading to pretty high caloric density

“Source of protein! - has some protein in it, perhaps more than another product in the category, but protein still is probably less than 50% of the carb content by mass, and also has fat. Never mind the quality or bioavailability of the protein.

Protein is starting to enter the zeitgeist as something that is helpful for muscle maintenance during weight loss and for helping with satiety. But like anything, if you don’t pay attention, reading the ad copy not going to help reach your goals.