Americans have been told for years that they can lose weight by cutting the amount of fat they eat. The low-fat food craze of the past two decades has not produced a noticeably thinner population. Nevertheless, food manufacturers have developed artificial fat to reduce the calories in foods like potato chips. Now a new study from Purdue University has found that rats given Olestra-containing fat free potato chips as part of their otherwise high-fat diet gained more weight than rats eating regular potato chips and the same high-fat food. While we can’t generalize from rat studies to human beings, the researchers suggest that the chemical manipulation of food may not produce the expected weight loss outcome.