Alexa Schmitt, RD, a clinical nutritionist at Massachusetts General Hospital, says mono-unsaturated and polyunsaturated fats are "good fats" and that saturated fats can be consumed in moderation. Trans fats, however, should be avoided altogether, adds Schmitt, explaining that trans fats are dangerous because they raise cholesterol levels. High levels of certain kinds of cholesterol, in particular low-density lipoprotein (LDL) cholesterol (the so-called "bad cholesterol") increase your risk for heart disease and other health conditions, including stroke.