The phrase "popular fad" refers to something that is currently trendy and favored by many people, but is likely to lose its popularity and fade away over time. Full definition
It's a recently popular fad diet that is suggested to be the best solution for overall health benefits. (dietsinreview.com)
The keto diet is a very popular fad diet that relies on a state called ketosis, which is normally a state of starvation. (rawsomehealthy.com)
Indeed, most popular fad diets that have come and gone over the years have enthusiastically promised that you don't have to count calories, that you don't have to eat less, or maybe that you -LSB-...] (straightforwardfatloss.com)