Host: What are trans fats? Elizabeth Rahavi: Trans fats are originally developed to replace the highly saturated animal and vegetable fats that were being used in frying, baking and spreads. However science have shown that Trans fats have a similar effect on LDL or bad cholesterol that saturated fats do. And they also have a potential to reduce your HDL or good cholesterol. Because of this trans fats have been removed from most food products today.