Which kind of fat is worse? My highschool biology teacher said saturated fats were worse because saturated fats are more rigid. For example, vegetable oil (unsatured) is a liquid at room temperature, but butter (saturated fat) is solid at room temperature. My university chemistry teacher said unsaturated fats are worse because they are more reactive and tend to bond to things to make thick substances (sort of like the alkenes in gasoline make thick gunk that forms in the carb of your car if you don't drive it for a while). He gave the following example. If you eat saturated fats that are 100 carbons big (just for example), that saturated fat will not bond to anything and will stay 100 carbons big. If you eat unsatured fats that are 100 carbons big, the fats may bond to other things to make substances that are much bigger; say 200 carbons big. I don't follow health issues too closely and both teachers lack credibility in their own way.