There are good fats, and then there are not so good fats ... but it is a bit more complex than that.
Some good fats can do bad things (go rancid), and sometimes, a fat will sacrifice its goodness to keep another fat from doing harm.
Take for example, a recent study that looked at what happened when avocado was added to a heart-stopping American favorite, the hamburger meal.[i]
Researchers at the UCLA Center for Human Nutrition took eleven healthy subjects, and on two different occasions, fed them either 250 gram hamburger patty alone (ca. 436 cal and 25 g fat) or together with 68 grams of avocado flesh (an additional 114 cal and 11 g of fat for a total of 550 cal and 36 g fat).
The researchers then measured the degree of vasoconstriction following hamburger ingestion 2 hours later in test subjects given a hamburger meal either with our without avocado. The hamburger meal resulted in significant vasoconstriction, whereas the avocado+hamburger meal saw no change at all.