If the thought of trans fats—vegetable oils that have been converted (hydrogenated) to solid fat—makes you cringe, you’re not alone. Food manufacturers love this fat because it extends a food product’s shelf life and makes packaged foods creamier or crisper, but this nutrient has absolutely no redeeming value. In fact, trans fats lead to clogged arteries, cancer and diabetes. Step away from the Oreos, kids!

The news is even worse for bodybuilders: Trans fats not only prevent the body from using essential omega fats properly but can also enhance muscle breakdown, limit growth and even increase abdominal fat.

Your best move is to religiously read nutrition labels and make sure any food you eat contains zero grams of trans fats—right? After all, as of 2006 the Food and Drug Administration made it mandatory for food manufacturers to list trans fats content of packaged foods. Yet ensuring that you get less than the 2-gram daily maximum of trans fats recommended by the American Heart Association (AHA) can be trickier than it seems. That’s thanks to a loophole in labeling laws allowing food manufacturers to label foods as containing “zero trans fats” if the trans fats content is less than 0.5 gram per serving.

You read that correctly: If a food contains up to 0.49 gram of trans fats per serving, it will read as zero grams of trans fats on the label. Okay, that’s not all that big a deal if you consume only one serving. But given that serving sizes are often minuscule and bodybuilders need more nutrients than the average couch potato, eating five servings of that food per day has been known to happen. Those five servings could serve you up to 2.45 grams of trans fats, slightly more than what the AHA recommends and way over what M&F recommends—our zero means zero!

Congress is already pushing legislation called the “Trans Fat Truth in Labeling Act” that would call for food manufacturers to place an asterisk next to the zero grams of trans fats listing if a product contains any amount of trans fats. This would notify consumers that a serving of that food could contain up to half a gram of trans fats. But it may be awhile before this takes effect, if ever.

In the meantime, here’s how to ensure that your trans fats intake stays at true zero: Don’t just look for the amount of trans fats listed on a label, read the ingredient list. If you see the terms “partially hydrogenated” or “hydrogenated” oil of any kind, drop the food and walk away. Those terms mean the food contains trans fats, even if the label claims otherwise.