“Diet” snacks usually contain some sort of fake fat or sugar — a synthetic substitute that helps make the food taste as sweet or as rich as the real thing, but without the calories. The thinking is that eating fake fats will help dieters lose weight.
Rats and Pringles
Apparently not, at least if you’re rat. Researchers from Purdue University conducted an experiment [PDF] in which they divided rats into two groups: one was fed a diet of high-fat rat pellets and the other standard low-fat chow. Both groups of rats were further divided. Half of each group was given regular high-fat Pringles potato chips along with their rat food; the other half of each group was sometimes given regular Pringles and other times given low-cal Pringles Light potato chips, which are made with the synthetic fat substitute olestra. (Olestra passes through the body without being digested, so it’s got zero calories.)
The researchers found that the rats on high-fat chow that were sometimes fed “light” potato chips ate more overall and gained significantly more weight and body fat than the high-fat-chow group that got only the full-fat chips. What’s more, these rats didn’t lose weight after the fake-fat chips were removed from their diets.
Meanwhile, neither subgroup of rats on low-fat chow gained any significant excess weight. But when these rats were switched to the high-fat diet, those that ate the fake-fat chips gained more weight and body fat.
It’s always tricky extrapolating the results of rat studies to humans, but previous research suggests the same phenomenon could be seen in people. As David DiSalvo explained at Forbes.com:
The reason this happens is that the brain, for all its wonder, can be duped. Artificial fat elicits similar biological responses as real fat, including increased salivation, hormonal reactions, and metabolic changes. In other words, the brain is gearing up the body for a burst of calories. When the calories don’t arrive, the brain panics, so to speak, and kicks into starvation mode by converting even more calories into fat.
Past research found that eating artificial sweeteners catalyzes a similar effect. The brain is signaled by the taste of the sweetener to expect a load of calories, and when they aren’t delivered the fat storage process accelerates.
Bottom line: if you don’t want to gain weight, you’re probably better off sticking with naturally low-fat, unprocessed foods like whole grains, whole meats, fruits and vegetables.