Some trans fats occur naturally in small amounts in some meats and dairy. (You don't need to be concerned about these. Some of the trans fats found in animal sources like CLA have been shown to be good for you.)

In manufactured food, if the ingredients list contains the words "fully hydrogenated ..." then there should no trans fats left (or negligible amounts). Fully hydrogenating a fat just turns it into a saturated fat, similar to a saturated fat that would occur in nature.

If the label says "partially hydrogenated ..." than it would contain potentially harmful levels of trans fats. Check the label for the amount of trans fat content. Unfortunately if it's less than 0.5 g per serving they can list it as 0 g. And if the serving size is small, you could potentially be looking at significant amounts of trans fat.

Unfortunately, if the label doesn't say fully or partially, but just the words "hydrogenated", then there's no way to know if it's full or partial hydrogenation. It could be either. (BTW, in some cases on the internet I've read that people have written to the manufacturers of Kraft Peanut Butter and Armor Lard to find out if their "hydrogenated" ingredients were fully or partially hydrogenated, and both responded that it was fully, and the amount of that fully hydrogenated ingredient was very small. I don't know why they don't just list it as fully hydrogenated then to avoid confusion.)

The good news is that many restaurants and food manufacturers have been eliminating the use of partially hydrogenated trans fats, and so human consumption has been going down steadily. Unfortunately instead of replacing these with fully hydrogenated or naturally occurring saturated fats, they've been using Omega-6 vegetable oils. Sigh. Maybe someday they'll get it.

I've noticed a few foods that still contain high amount of trans fat at the supermarket. They are:

1. Some margarine brands (many brands of margarine have eliminated trans fats, but some still rely on them like Parkay. You should be using real butter anyhow.)

2. No name or store brand shortening or lard (these are the worst offenders. Some ungodly amounts of trans fat in these. However, please note that Crisco brand shortening has changed their recipe and is virtually trans fat free now. Most brand name lards are also fine. Their labels will list a very small amount of trans fat, like 0.1 or 0.2g. I wouldn't worry about this. Butter has more naturally occurring trans fat: 0.5g.)

As for restaurant food, the worst offenders used to be things like donuts and pastries, and fried foods, but like I said, many places have been eliminating the use trans fats. You need to check with them to see whether or not they are still using partially hydrogenated crap.