Since the 1950s, health and mental health professionals have criticized the conventional wisdom that permanent weight loss is possible. Clinical trials on weight loss have high dropout rates and rarely have participants move from “clinical” to “normal” body mass index levels, and the overwhelming majority of people who lose even 5–10% of body weight have regained it 1 year later. The present article reviews some methodological issues in the weight loss literature and provides some possible reasons why psychologists continue to uphold the conventional wisdom that permanent weight loss is possible.”