All in all, these fats are bad. They are not good, even in small amounts, there is no benefit to their consumption, and I recommend you do your best to eliminate them altogether from your diet. Trans fats are created by a process called hydrogenation, which, to summarize, changes the chemical composition of a fat from being liquid at room temperature to solid.
There have been serious health concerns with trans fats, which have led to their ban in consumer products. Consuming 2% of your daily fat intake as trans fatty acids has been shown to increase the risk to your cardiovascular health by 23%! So, the good news is that trans fats are no longer rampant in our food system; however, they can still be found in deep fried foods, as they can be formed from frying oil. Although fried foods may taste yummy, it is important to limit our consumption and consider fried foods to be a treat, not a dietary staple.
Tip: Stay away from margarine. Instead, try mixing equal parts butter and extra virgin olive oil. Keep it in the fridge and it will be just as smooth as margarine and taste much better.
Saturated fats are typically known as animal fat, and for being solid at room temperature. I do not want to demonize saturated fat as it does not compare to trans fat, however, it is not a fat that we advise eating liberally. There is research to suggest a high consumption of saturated fat is linked to cardiovascular disease; however, our bodies do need saturated fat in moderation, so choose good sources.
There are sources of saturated fats, such as coconut oil, that have some promising benefits, however more research is needed before any health claims can be made.
Tip: Saturated fats are found in abundance in animal products, so try making one meal a week vegetarian or fish—try a salmon burger instead of beef.