FATS- NOT A FOUR LETTER WORD
First of all, the word "fat" has been grossly mistreated and misused over the years and enough is enough. Fats are not the enemy. You just have to choose your fats wisely, just like your friends. So, let's discuss, there are two main subsections of fats: saturated fats and unsaturated fats. Fats, both saturated and unsaturated, provide you with fat-soluble vitamins A, D, E, and K, all of which participate in important functions in your body.
Saturated fats, the kind that are found in meats and meat products, dairy and dairy products, and certain oils like coconut (GASP!) and palm kernel, are not really your bestie, but more like a frenemy. They're fine, beneficial even, but in small amounts. I’m not saying to cut them out completely, they certainly have a place in a balanced diet, but years and years of a high saturated fat diet could (and likely will) raise your LDL cholesterol*, and put you at a higher risk for heart disease and all kinds of other ugly health problems. I know, not cool.
Now on to the good part, the unsaturated, or what have been known as "healthy" fats.
These are the fats that are found in avocados, olives and olive oil, fish and seafood, nuts and nut butters, seeds, tofu, etc. These, like all good things, should be an important factor in your diet, but they do have limits as well. The Institute of Medicine recommends 20% to 35% of your calories per day come from unsaturated fats. So, go ahead, get the guac, who cares if its extra?
*LDL stands for Low Density Lipoprotein and is the "bad" cholesterol you hear so much about. The other, is HDL, High Density Lipoprotein and is considered the "good" cholesterol. This is because these two do very different things in the body. One helps, one hurts. My trick to remembering the difference between LDL and HDL cholesterol... think LD "less desirable" and HD "highly desirable".