But it's there in the OP, and there at the very top of the article linked in the OP which is the topic of the thread if you'd bothered to click on and even glance at it.
Not only do people apparently gain weight four times faster than people who have lost it by other methods, but people on WLI are also said to lose more lean muscle while dieting (around 40% of the weight lost is lean muscle, while it's around 20-25% of the weight by regular dieting).
The concern would be you lose lean muscle, go off the WLI, and regain four times faster. Go back on the WLI, and then lose even more lean muscle. This muscle loss sets people up for future health problems, particularly older people whose muscle mass has deteriorated already with age and lack of use. Also worth bearing in mind, the heart is a muscle...
And at any point you may pick up a bonus longterm health problem such as pancreatitis, serious GI tract, gallbladder, or kidney problems, vision loss, or bowel perforation.
The benefits would probably outweigh the risks if you were morbidly obese, and had good guidance. But it's clear women of normal weight and those who are only modestly overweight are on WLI with little to no supervision.
However, anyone who wants to discuss WLI in anything other than glowing rapturous terms is called bitter, jealous, spiteful, and my favourite, "seething," all of which is surely projection, and a posse of posters engage in a group effort to bully them off such threads.