“Nutrition” bars — we use the term loosely — show up in movies in the oddest ways. In “Mean Girls” (starring Lindsay Lohan), they're fobbed off on an unsuspecting clique of popular girls as weight-loss snacks, when in fact they're designed to pack on pounds.

And in “Snowpiercer” (starring Chris Evans and Tilda Swinton), a sci-fi flick about a post-climate change world, they're gelatinous protein blocks made from insects.

Sadly, those may not be much better than what's available today.

A report by Consumer Lab found that many bars aren't as healthy as they claim. The report analyzed the nutritional content of 17 top-selling bars and found that they often contain more carbs than listed on the nutrition panel. In fact, one had 57% more.

Some are also high in fat and cholesterol. One had 22% more fat — mostly saturated fat — than listed, along with twice the cholesterol.

Others are too low in fiber. One contained only 62% of the fiber listed.

To be a smart shopper, read the nutrition panel and look at the list of ingredients. Bars that declare “net carbs” are often hiding their true content.

For instance, if the wrapper of a bar says net carbs total only 2 grams, but the Nutrition Facts panel shows 20 grams of carbohydrates, there may be 18 grams of sugar alcohols (such as erythritol) in the bar.

You should also skip bars that contain tapioca starch, which is not a good fiber source.