Because for several decades now, the research clearly shows about 99 % of people who lose weight on a weight loss diet gain it back again within a year. (psychologyofeating.com)
And although you might lose a few pounds while on this said diet or cleanse, you are sure to gain it back in less time than it took you to lose the weight. (thinmdmedspa.com)
After all, what's the point in losing 20 lbs in 2 months if you just gain it back anyways (and with a now sluggish metabolism from the huge calorie deficit)? (coachcalorie.com)