The FAQ is particularly informative.

It's amazing how such a small amount of trans fats can cause so much of a problem.

It's hard to find any prepackaged foods in the USA in a regular grocery store without partially hydrogenated oils in them.

And unfortunately some pre-packaged low-carb food has them. For example Carb Solutions Creamy Chocolate Peanut Butter bar has Partially Hydrogenated Palm Oil in it, but you can't tell how much because the total fat is shown at 10 g and saturated fat at 3.5 g, but no other information on the label.