Remember olestra, the fake fat marketed under the name "Olean" that was all the rage a few years back?

It was supposed to turn belly-bursting snacks into low-fat treats, but public tolerance for this stuff quickly pooped out: Its side effects include severe diarrhea and the infamous "anal leakage."

Olestra isn't as widely used as it once was, but it's still a key ingredient in "low-fat" and "light" versions of popular potato chips. And it turns out eating those "light" version could have very heavy consequences.

Researchers randomly gave a group of rats either normal potato chips – which are plenty bad enough on their own – or a mix of normal chips and chips with olestra.

No word if the olestra rats got the runs – but they did get something else: big rodent bellies.

The researchers let both sets of rodents eat as much as they wanted of either a high-fat or low-fat diet, and found
that the fat-eating rats that got olestra didn't know when to stop.

They just kept right on eating, gained weight, and developed more fatty tissue as a result. 

Rats on a low-fat diet didn't have the same problem – at first. But once fats were put back into the diet, they joined the pig out (or is it a rat out?) and kept eating as well.

Here's the most frightening part: When potato chips of all kinds were taken off the menu, the rats didn't lose the weight.

In fact, they kept right on overeating.

Sound like anyone you know?

Gullible dieters spend billions a year on snacks that claim to be "low-fat," "light," and "low calorie" – but none of them ever seem to lose any weight, and many of them actually pack on more pounds than ever before as they load up on this supposed diet food.

That's true whether the treats contain olestra or not – because supermarket snacks and fast-food treats are almost always packed with even worse ingredients, including deadly processed carbs such as "fat-free" sugar.

Bottom line: Whether you're a rat or a human, the only way to lose the weight is to skip the snacks – no matter what promise is made on the label.