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The Kinds of Fats

And Why It Matters To You

Fats and Oils

Fats can be either solid or liquid. Solid fat, like lard or butter, is usually saturated. Liquid fat, like vegetable oil, is usually unsaturated. The definitions of these fats come from the patterns of chemical bonding between the carbon atoms of the fatty acid "tails," and the bonding of hydrogen atoms to those carbon atoms.

Saturated Fats

In saturated fats, every carbon of the "tails" is bonded to the carbon atoms on either side, and to as many hydrogen atoms as possible. Therefore, it is reasonable to say that the fatty acid is "fully saturated with hydrogen atoms." A segment from the hydrocarbon tail would look like this:

Unsaturated Fats

Unsaturated fats have two or more "missing" hydrogen atoms. The relevant carbon atoms, instead of forming one bond between the carbons, form two bonds -- a double bond. If the carbon atoms are busy double-bonding with each other, then they aren't forming bonds to hydrogen atoms. There are not as many hydrogen atoms as possible in the fatty acid tail. We could represent it like this:


That's pretty much it. Saturated fats are saturated with hydrogen atoms. Unsaturated fats are not.

But there are different varieties of unsaturated fats. Mono-unsaturated fatty acids have one C=C double bond. Poly-unsaturated fatty acids have two or more C=C double bonds, usually two, but sometimes three or four. Because of the possible variations, it has been necessary to develop standards for naming different unsaturated fatty acids. The easiest naming system to remember gives names like ω-3 and ω-6. However, to talk about these different variations, it is very helpful to simplify the diagrams, so they aren't all cluttered with C's and H's.

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