Snake Oil: From an advertisement on Slate, a weight loss pill for "pre-menopausal and post-menopausal women" (that covers everyone):

The results were astounding! Group A (the Estrin-D group) experienced a significant decrease in overall body weight - an incredible 1603% more weight loss (over 16 TIMES more) than those who took a placebo - without following a complicated diet program or following a prescribed exercise regimen. In other words, the active ingredients in Estrin-D reduced caloric intake automatically.

The active ingredient is a "powerful xanthine," the stimulant in caffeine. 1603% more weight loss is almost impossible to believe. It's got to represent a very small change magnified by percentage differences. Say, if the control group lost 0.01 pound on average and the test group lost 1 pound. If nothing else, the supplement industry has learned the lessons of how to manipulate numbers well.