There are various ways to look at the word “fat.” Most of us think of the word with pejorative overtones, something we don’t want applied to us. The adjectives aren’t pretty and evoke feelings of playground humiliation: chubby, flabby, plump, chunky, pudgy. Then of course you could think of “fat” like that fat check you got when you finally sold your Van Halen live-in-concert VHS collection on Craigslist. And don’t even get me started on “phat” (mostly because, even as a child of the ’90s, I still don’t think I get it.) But there’s another set of terms I want to talk about today. Terms like lipid, adipose, triglyceride, sterol, fatty acid. These describe the other kind of fat, the macronutrient every human being requires to sustain life. There are so many fascinating aspects to dietary fat and the way our bodies use it, and quite possibly a lot you didn’t know.
As I’ve progressed in my coursework toward becoming a Dietetic Technician, I’ve come to understand so much of what always seemed confusing about fat nomenclature. Since I’ve learned how to navigate the different kinds of fat (like that mental image?) I thought I’d share some of the information I’ve found interesting and helpful.
1. Let’s start with an cool trivia point: what’s the fattest organ in your body? Your brain! About 60% of your brain’s matter is fat. So if someone calls you a “fathead,” you can be proud to know you’re perfectly normal. (And they’re a fathead, too. Obviously.)
2. Fat provides 9 calories per gram (whereas carbs and protein provide 4). This is true across the board for any fat. That’s why, even though nutrition labels list number of calories from fat in a food, you can always calculate it yourself by multiplying the grams of fat by 9.
3. What’s the difference between saturated and unsaturated fats? You probably know they must be related because they have that word “saturated” in common. To understand the difference between these types of fat, you have to understand what “saturated” means. Fat is made up of carbon chains. In saturated fat, all of the available carbons in the chain are bonded with hydrogen…kind of like how I always felt at junior high dances when all the cute boys immediately paired up with the popular girls. All the carbons are taken, paired off, saturated. In unsaturated fats, however, there’s a break in the music, a chance for a different kind of bond. Instead of all the carbons being taken up by hydrogen, something called a double bond occurs, which, instead of bonding a carbon to hydrogen, bonds carbon to another carbon, leaving it not entirely saturated…in other words, unsaturated. And the only difference between a monounsaturated fat and a polyunsaturated fat is that a mono has only one of these breaks, whereas a poly has two or more.
4. Now that you know the difference between saturated and unsaturated fat, it probably makes sense why saturated fat is generally solid at room temperature. Everything is paired off and packed in, making it denser. On the other hand, unsaturated fats (like oils) are generally liquid at room temperature for the opposite reason.
5. What about trans fats? What are they and why are they so scary? Somewhere along the line, scientists realized that they could mess with the chemical structure of unsaturated fats (i.e. oils) by plopping in some extra hydrogen where it didn’t really belong to create what are called trans fats. The process of unnaturally adding hydrogen is known as hydrogenation. So when you see the word “hydrogenated” on an ingredient list, you know the food contains some amount of trans fat, even if the label says 0 grams trans fat. (The FDA allows foods with .5 grams or less per serving to round down to zero.) Research has yet to show exactly why trans fats have a negative effect on health, but they have definitively been linked to coronary heart disease and several other conditions you don’t want to get.
6. One last kind of fat you hear a lot about is Omega 3s. The reason these unsaturated fats have this name is simply due to the spot where they have their carbon-to-carbon bond: on the third carbon from the end. Bet you can guess where Omega-6 and Omega-9 have theirs now, too.
Okay, that was kind of a lot of chemistry. I should probably stop now. But I have so many more things I want to tell you about fat! I’ll be hoarding up my fat facts for another post soon, focusing on fat’s effects in your body. And if you’re still hungry for macronutrient info, you can head over to my carbohydrate facts page!