Unless a physician tells you otherwise, there's no reason to avoid all types of fat in your meals and snacks. The ones from plant sources known as monounsaturated fatty acids (abbreviated as MUFA) should be part of the healthy foodie's diet. The fat in many types of fish is also essential for your health and well-being.
Conversely, we should minimize or avoid "bad" fats, which include those from animal sources--found mostly in meat, poultry and dairy products--as well as the largely man-made stuff known as trans fats that extends shelf life in a range of processed foods.
This posting is about what we should be eating, and less about what to avoid, so I'll make the avoidance part brief. For packaged foods, read labels. If the ingredient list includes the words "partially hydrogenated," put the thing back on the shelf and step away! Avoid fatty cuts of meat--or avoid meat/red meat altogether; remove all skin and visible fat before you eat meat, fish or poultry; choose fat-free or low-fat dairy products.
OK, enough of what not to do. Here are some of the fats we CAN and SHOULD eat. Of course, fat of all kind has more calories by weight than do the other food groups (proteins and carbohydrates), so if weight control is an issue, be careful not to overdo.
AVOCADO not only tastes marvelous, it also is a very healthful food.
NUTS of all kinds are loaded with MUFA and satisfy hunger longer than many other snacks; add nuts to cereal and/or salads for a MUFA boost.
OLIVE OIL as well as CANOLA OIL are great for you. The lauded Mediterranean diet is based on cooking with olive oil -- and eating it on bread (instead of butter or margarine) and salads, among other uses. Olive oil is our go-to oil for dipping and for salad dressings, while I usually cook with canola oil thanks to its higher smoke point. (It works better for stir-frying or sauteeing, I find).
Fats are satisfying to the palate and help to make you feel less deprived, if you're trying to lose weight. So don't go fat-free as you combat any fat on your body that you'd like to shrink.