It is true that much of the commercial weight-loss industry is composed of charlatans who lack evidence to back up their come-ons. But that's not the same as saying that there is no way to reduce one's body size sustainably.
As you know, I did (am doing) it, and I have lots of friends who have as well. But there's also the long-term, legitimate, National Weight Control Registry, which is coming up on 20 years and tracks more than 10,000 people who've lost significant weight and kept it off for significant time.
Weight loss often doesn't result from stupid dicta such as "eat a ton of cabbage soup and on Tuesday eat as many bananas as I want but nothing else," as the HAES crusader Ragen Chastain puts it mockingly in her recent post. Nor is weight loss is not the sole precursor to health.
But weight loss is possible, is sustainable, and is almost always a positive development, on balance. I have sympathy for those who put so much energy into arguing otherwise, and (think I) understand its source, that if it hasn't happened for them, it can't happen.