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 an analogy today that is fantastic. We're all generally familiar with the idea that we can burn sugar (or glucose) for energy, right? I think many of us are less familiar with the notion that we can also burn fat for energy. Think of lighting a charcoal fire with a few twigs and sticks. The twigs and sticks will catch fire really quickly, and burn out really quickly. The charcoal won't catch quite as quickly, but once it does catch, it will burn for a really long time. Using that analogy: our bodies burn sugar like the fire burns twigs; and our bodies burn fats like the fire burns charcoal.
Immune System: many molecules involved in fighting infections in the body are made up of fats.
Why are People Afraid of Eating Fats?
To be too brief, there was a study published in the mid 1970s - the Minnesota Coronary Experiment - led by Ancel Keys. This study concluded that saturated fats caused heart disease; though it is now quite well-understood that much of the data from that study that would conclude otherwise was never actually published (see the article I referenced in the first paragraph of this post). That was the first vilification of saturated fats. It's been since then that we've seen a rise in the use of omega-6 fats and trans-fats in our food supply. This and other research eventually led us to believe fats cause heart disease by causing plaque build up in the arteries. The truth is, we are still trying to understand exactly how plaque build-up occurs. It is true that fats are involved in the process of repairing damaged cells (which is the beginning of the biological process behind plaque build-up...the artery wall gets damaged and the body tries to repair it!), but it is certainly not clear that fats cause the initial damage to artery walls. Rather, it is much more likely (read: true) that oxidized molecules (glucose, for example) cause the initial damage to the artery wall, and the fats are simply there to try to fix it! Yes, however, if your diet is extremely high in fat (and your lifestyle extremely low in movement), these molecules are sticky, and if you have that initial aterial damage, you could cause yourself excessive plaque build-up simply because you're eating so many fats and not utilizing them.
Oh, and, people tend to think that eating fats = storing fat on your body. This, simply, is not true. What is true is that if you take in more energy than you expend (fats, carbohydrates, or proteins), you will likely store fat on your body. If you eat a normal amount of fat (anywhere from 20-50% of your diet for an average, active individual) and you don't overeat (and you're generally in good spirits and low in stress), you simply will not store fats the fats you eat as fat on your body; no, you will use those fats for all of the purposes listed above.
What Foods Contain "Good" Fats?
Now for the gold. "Good" fat foods generally consist of nuts, seeds, eggs (yeah, that cholesterol, necessary), salt-water fish (salmons, mackerel, sardines, cod), animal fat (if the animal ate green grass), olives and olive oil, coconut and coconut oil, avocados and avocado oil.
What are "Bad" Fats Anyway???
It is definitely one of my favorite things to say to say that no food is bad for you. Too much of anything can be bad for you. Too much of a good thing can be bad! You can overdose on vitamins, you can overdose on minerals...and they can become toxic to your body! Woah now. So, if you eat real food and you eat a variety of it and you don't overeat any one thing, then no food is bad for you.
Trans fats are the "bad" fats. Trans fats are not found in nature; no, they are not natural. Trans fats are made in a lab. They were developed in response to the "fear of saturated fats" craze. How are trans fats (man-)made? You take a fat that is normally liquid at room temperature (unsaturated fat) and you change the orientation of the double bond so that the kink is much less noticeable...so that you can force the otherwise liquid fat into a now solid structure. See?
You're familiar with margarine, I imagine? Margarine is made by taking liquid fats and forcing the double bonds to flip their orientation, now making them solid fats. Eek. Seems like that might be a challenge for the body to digest...ya think?
Well, that's Lipids 101 folks. Not exactly what I'd set out to write about. But it serves as a decent foundation for understanding fats anyways.
Here are some of my favorite fat foods:
Nuts, avocados, salmon, olive oil, eggs, and olives (not pictured)!
I choose to eat a diet that contains approximately 30% fat. I. love. fat. And so should you.