By concentrating on holistic wellness, Weight Watchers hopes to be associated with a movement that will last a long time, as opposed to many of the diet trends that have come and gone in the previous 20 years.
According to Google Search Trends, one of the first popular diets, the Atkins diet, was still highly popular in the late 1990s and early 2000s before falling into oblivion around 2004. The palaeolithic, or caveman, diet gained popularity in 2011-12, and the ketogenic (keto) diet was arguably the most-searched-for diet of the previous decade, rising in popularity owing to celebrity endorsements.
Of course, in addition to the more extreme "buzzy" diets, there are also far larger shifts occurring in our eating patterns, with an increasing number of individuals adopting gluten free, vegetarian, or vegan. Taking advantage of such trends while yet appealing to the broadest possible audience would be difficult for WW — even with Oprah as a spokesperson.
Source: Google Search Trends, chartr