Trans fat
For some time, the US government's "Food and Drug Administration" allowed makers of food products to label their products as having "0 grams of trans fat per serving" as long as the amount of trans fat in the food product falls below 0.5 grams per serving. Since partially hydrogenated oils are the major source of trans fat, reading the "ingredients" label is the safest way to ensure that a food does not contain any trans fat at all. Fried foods will likely, but not necessarily, contain trans fat since fried foods are produced by using very hot oil.