Just Plain Fat
There is so much to say about fats, I hardly know where to begin. I'd originally set out to write about saturated fats, since, as you may have noticed, saturated fats are finally getting the vindication they deserve in major media channels (primarily in relation to this article published in the British Medical Journal in April). But then I came across a video that totally excited me: Cereal Killers II, a super well-made video about a world-class triathlete and his wife as they prepare to row across the Pacific Ocean on a predominately fat-based diet. (I watched the movie here, but you can also purchase the video from the producers here.)
So now I'm like, what do I say?
Let's start with some basics. Fats. Fats: what are they? why do we need to eat them? why are people afraid of eating them, still? what foods contain "good" fats? and what are "bad" fats anyway?
Well, we might as well go through, question by question.
What Are Fats???
Fats are one of your three macro nutrients (the other two being carbohydrates and proteins). The term macronutrient refers to the molecules in our foods from which our bodies can derive energy. Fats are molecules containing Carbon, Hydrogen, and Oxygen (hmm, just like a basic sugar molecule). Of course, the atoms of fats and sugars are arranged very differently, thus causing the two to have very different functions within the human body.
Below is an image of a triglyceride. Maybe you've heard this word before at your doctor's office. Maybe you've been warned of your triglyceride levels being too high. Triglyceride is the scientific term for "fat". A triglyceride is composed of three fatty acid molecules and one glycerol molecule (the glycerol is the vertical chain of three carbons on the left, and the three fatty acids are the three horizontal chains of carbon atoms on the right).
Here's what a triglyceride might look in three dimensions. The red part is the glycerol and the black-and-white chains are the fatty acid chains.
So maybe you haven't heard the term triglyceride before and now you're more confused. For the most part, you can probably forget that word (but not really), and instead understand the different types of triglycerides out there, whose names are probably much more familiar to you. Triglycerides are categorized as saturated, monounsaturated, and polyunsaturated. Well, to be real, fatty acids are categorized as saturated, monounsaturated, and polyunsaturated (from now on I will use the abbreviations SFA, MUFA, and PUFA, respectively, to refer to the different types of "fats").
I'm gonna guess you've heard these names before. But what do they mean. Jeez! Quite simply, the level of saturation of a fatty acid molecule refers to the degree to which the carbon atoms in the fatty acid chain have bonded with hydrogen atoms. Scroll back up to the first image...see how the top two fatty acid chains are in a straight line, and the bottom fatty acid has a kink in it? The kink is even highlighted in green. The top two chains are saturated; every carbon in the center of the chain (so, excluding the very last carbon and the very first carbon) is bound to two hydrogen atoms. That is the maximum number of hydrogens that those middle carbons can bind. Now look at the bottom chain; remember it has a kink in it. What do you notice about the two carbons immediately on either side of the kink? They are each bound to only one hydrogen. And those two carbons are now sharing two bonds between them (remember from high school biology, this is called a double bond). The double bond creates a kink! And, since those two carbons in that bottom chain are only bound to one hydrogen apiece (when they could be bound to two!), those two carbons are not saturated; in fact, they are unsaturated. Thus, the entire fatty acid chain is considered unsaturated. Monounsaturated refers to the fatty acid chain having only one double bond; polyunsaturated refers to the fatty acid chain having more than one double bond.
Food fats are then classified as saturated, monounsaturated, or polyunsaturated based on a majority rule. So, whichever of the three types of fats is most abundant in that food, that's the classification it gets. Nearly all food fats contain some combination of SFA, MUFA, and PUFAs.
Scroll back up that top image one more time. Notice the kink in the unsaturated fat again. Notice how the saturated fats are in a straight line. This tells us something about how these fats affect the shape of the foods they are in. Saturated fats tend to be solid at room temperature (because the fatty acid chains make nice straight lines that are easily stackble into a solid structure). Unsaturated fats are typically liquid at room temperature - remember the kink. Think of trying to stack a bunch of kinked fat molecules...good luck! Those little buggers don't want to pack up nicely in to a block; no, they want to free like water...or, oil.
In food speak, we typically use the word oil to refer to liquid fats. Most oils contain unsaturated fats.
Butter: solid: saturated. Yum.
Coconut oil??? That's a tickster. But remember, most fat foods contain a combination of SFA, MUFA, and PUFA. Coconut's a great example. It contains both saturated and monounsaturated fats. It is solid at lower temperatures, but the fats quickly turn to liquid with even just the slightest heat.
So, that's saturation in a nutshell folks. Seriously, a nutshell.
Why do We Need Fats?
Fats play so many important roles in the body I can hardly begin. Let's see, well, every single cell in your body has what is called a phospholipid bilayer that serves as the cell membrane. Notice anything about that word? Lipid, maybe? Lipid = fat. Therefore, every single cell in your body contains an outer membrane that is composed of fats (and proteins)! Well, that seems important.
Hormones: many of these are made of fats, including your reproductive hormones.
Vitamin D: our bodies make vitamin D using cholesterol (technically a fat) as the starting molecule!
Your brain: the tissues in your brain are made up of fats! Your nervous system is made up of fats! Think about any time you...do anything...your body requires fats to transmit the messages!!!
Digestion: you got it folks, we need fats to digest our foods! In particular we need fat to digest fat! Woah!
Vitamin and Mineral Transportation: many vitamins and minerals are fat-soluble (and therefore not water-soluble; our blood is water!) and therefore require a fat molecule to transport them through the blood to the body cells so they can be used!
Energy: here it is. Our bodies can burn fat for energy. I heard