Fake-Fat Confusion

Why switching from the real thing to a low-fat or low-calorie substitute can pack on the pounds.

potato chips

Although foods featuring fat substitutes may promise all the taste with none of the guilt, a study published in Behavioral Neuroscience suggests that such products might actually encourage weight gain, not weight loss.

In the study, researchers gave two groups of rats access to potato chips. For one group, the chips were the regular high-fat, high-calorie variety; for the other group, chips were split between the regular variety and lower-calorie ones with olestra, a fat substitute.

While it might seem that the rats eating the olestra chips half the time would end up weighing less than the rats with access to only high-fat chips, the opposite was true, says lead researcher Susie Swithers, PhD, a professor of psychological sciences at Purdue University. “That group couldn’t figure out what to expect, because sometimes they ate something that tasted fatty and they got a lot of calories, and sometimes they ate something that tasted fatty and didn’t get very many calories,” she says. “They weren’t able to predict what was going to happen, so they ended up overeating, just in case it was a low-calorie food.”

Because our bodies often use such taste cues to determine how much to eat, it’s worth thinking twice before switching from the real thing to a low-fat or low-calorie substitute, says Swithers. “We tend to think that switching to a fat or sugar substitute will automatically lead to a reduction in food intake or to weight loss, but it may impair our ability to regulate our food intake,” she says. Eating healthy, natural fats — fats that don’t send mixed signals to our bodies — is a better option.


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