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Extra protein is unlikely to help you stay full, slim down, or build muscle. But if a bar is your mini-meal, you're better off with one that packs a good dose of protein.

The best protein bars are mostly real food, like nuts or fruit:

RXBAR. This up-and-comer leads the pack. That's because nearly every RXBAR is largely nuts and dates, plus enough dried egg white powder to hit 12 grams of protein (for around 200 to 220 calories). Too bad the chewy texture wasn't a hit with some of our taste testers.

Lärabar Protein. Think of it as a plants-only version of RX. Larabar Proteins start with the brand's blueprint—nuts blended with dried fruit—and toss in enough pea protein powder to roughly double the protein. (The calories and protein are similar to RX's.)

When it comes to protein bars, RX and Lärabar are some of the best. Here's how some of the rest stack up:

KIND Protein from Real Food. KIND'S protein bars have enough whole nuts to supply 7 or 8 of its 12 grams of protein. Nice! (The rest is from soy protein isolate and sometimes milk powder.)

The downside: KIND may sell the only "real food" protein bars with a candy-like coating drizzled on top. There's enough palm kernel oil to reach 3½ or 4 grams of saturated fat.

Perfect Bar. The hefty dose of honey in refrigerated Perfect Bars means around 4 to 5 teaspoons of total sugar. Along with a good dose of nut butter, each bar has around 300 calories.

And think of Quest and ONE bars as high-protein junk food. Yes, they're low in sugar because of sugar alcohols, sucralose, or stevia extract. But they have more processed protein and processed fiber than nuts or fruit. What's more, ONE's palm kernel oil coating tucks in a quarter of a day's sat fat.

What to look for in a bar

Fresh fruit, crunchy veggies, unsweetened yogurt, nuts, and other whole foods still beat protein bars and other snack bars any day. But if you want a bar that's more real food than candy, here's our guide to checking the Nutrition Facts label and ingredients list:

Real food. Look for more than a trivial amount of whole food—nuts, fruit, and/or intact whole-grain kernels—and little or no refined-grain flour.

Sugar. Look for no more than 7 grams (1½ teaspoons) of total sugar. Exception: for dried-fruit-based bars like RXBAR and Larabar, most of their sugar comes from fruit. (In other bars, most of the total sugar is added sugar.)

Low-calorie sweeteners. Look for bars that have no aspartame, sucralose, or acesulfame potassium. We rate all three as "avoid." (See our website Some bars cut sugar by adding (safe) stevia leaf extract and erythritol, which is less likely to cause gastrointestinal distress than other sugar alcohols, like sorbitol or maltitol.

Saturated fat. Look for no more than 2 grams. That knocks out nearly all bars that are coated or drizzled with chocolate- or caramel-flavored coatings. Both use sat-fat-rich palm and palm kernel oils to stay solid at room temperature.

Photos (top to bottom): nadianb/, Chicago Bar Company LLC dba RXBAR, Kaamilah Mitchell/CSPI.