The phrase "diet craze" refers to a popular and intense obsession or trend related to a specific way of eating or following a diet plan. Full definition
The low - carb diet craze was one of the most popular dieting trends in history. (dietsinreview.com)
The low fat diet craze that started in the late 1950's, left us fearing butter, and worse, switched us over to margarine and more processed oils. (salernocenter.com)