One of the biggest lies of fat acceptance is that diets don't work, and this is because after losing weight, they return to the exact same lifestyle that caused them to gain the weight in the first place. The problem is English uses the same word (diet) to mean both the way you eat normally, and a temporary regime you use to lose excess weight. Fats confusing the two (deliberately or not) is used as an excuse to make the claim that since weight loss from a "crash diet" isn't permanent, therefore changing your "lifestyle diet" doesn't work. This kind of mental ham-nastics is just one of the methods they use to claim they are helpless to change their weight.