Answer:
They do not keep lost weight off
Step-by-step explanation:
Fad diets are nutrition plans that are popular during a certain time period, often because they are promoted by celebrities, influencers, and misinformed fitness personnel, gaining their popularity by offering quick results with little to no effort. The drawback, atop sometimes being inherently unhealthy, is that without the implementation of interventions like increased physical activity and avoiding unhealthy dietary habits, the short-term results are not sustained and, thus, do not translated to improved long-term health; that is, the patients do not keep the lost weight off. This phenomenon is so commonplace that in some circles it has its own terminology: yo-yoing.
If using a "fad diet," the best practice is to fully research the diet, consider its benefits, risks, and consequences, assess if the diet can be followed on a sustainable long-term basis, and pair the dieting with a competent exercise regimen.