It also cites a study which says that the average loss is 5%. That isn't what most people imagine as "highly effective".
Weight also doesn't tell the whole story. The people don't get any better, they get (more) starved in addition to staying obese.
It's a disease with another cause, hunger is only a symptom.
Too much money has been wasted on proving and "educating" people that it's just overeating, while there is an overwhelming amount of evidence to the contrary.
The one that convinced me is horses. Horses get fat, and they need to wear a muzzle that makes eating difficult for them. Otherwise, they eat so much so fast that it literally kills them.
There seem to be AREAS that are affected and areas that are less affected. Either there are fat people in the area, or there are no fat peoplle in the area. People who move seem to quickly change weight to fit the local norm. There doesn't seem to be any clear correlation with dietary habits, or anything else that is commonly observed. The entire Japan appears to be spared.
It gets commonly missed that it isn't possible to get obese on purpose either. It's hard to eat more, and the body just seems to burn off the excess.