It is unfortunate that the fats that we eat which are divided into several fat categories are associated with being physically fat. That is to say, that if you eat a lot of fat, regardless of what the fat is made up of, that by virtue of this fact, you will create bodily fat. That simply isn't true, and the public would be far better off not associating products that are high in fat with being fat, because it is a simplistic association which is fundamentally wrong.
Dietary fats are broken down into monounsaturated fats such as olive oil, polyunsaturated fats such as corn oil, saturated fats such as whole milk, and trans-unsaturated fats such as pre-packaged snack foods. Each of these fats has definite chemical structures and in their natural state each is different than other fats, and hence their effect upon your body is different. In general, the only fat that is unquestionably bad for your body is the manmade trans-unsaturated fat typically made from hydrogenated vegetable oils which allow products to have much longer shelf lives and thereby prevents these food products from going rancid and thereby maintaining their form for extended periods of time. The problem with the manmade trans-unsaturated fat is that consumption of such takes a toll on the human body creating the propensity for cardiovascular disease as well as diabetes.
It is unfortunate, that there are so many products sold to people, that are labeled as low-fat, or no-fat, or similar, which gives the wrong assumption that low-fat products are somehow better for us as well as being necessary for us in order to reduce our bodily fat. This comes down mainly to false advertising, which tries to sell the impression that high-fat products such as nuts, fish, milk, and meat are very bad for you and will make you fat, whereas their low-fat versions are very good for you and will make you lean.
The most important thing to learn about dietary fat is that the health of the item that you are eating is dependent upon the processing of the product and the type of fat that it represents. For the most part, processed foods in which the chemical content of the food has changed or has been "enhanced" by that processing -- are foods that are going to be questionable as to their benefits, foods such as pizza, frozen dinners, and hot dogs, are foods that may well taste good but are only acceptable to eat occasionally. Whereas, foods such as your basic steaks, sardines, and eggs which are high in saturated fat are actually good for you.
Today's consumer is bombarded with all sorts of advertising, propaganda, misinformation, choices, and overall confusion when making decisions in regards to what they should or shouldn't eat. It is vital that consumers learn to ignore, for the most part, the fat content or percentage listed on a given food item, and instead pay close attention to the sugar content, and whether the carbohydrates are refined, and also the overall processing of the product before reaching for a particular item and purchasing it. For an absolute certainty, it is not the fat content of the product that you consume that will make you fat, but the sugar or sugar equivalent such as fructose that will.