We’re a nation of fatties – well at least that’s the popular view. Weight loss programs are scattered across the internet, TV, and (women’s) magazines.
So who do you believe? Which programs and/or diets work, and why?
Well, it’s not too hard to understand, if we go back to basics and look at the chemical reactions that occur in our body, what fat is, how it is made, and how it is removed. Like most things in life, there is a chemical explanation.
The first point to understand is that your body is an incredibly sophisticated chemical reactor that is able to convert very different chemicals into each other, with an efficiency and specificity that would be impossible in any laboratory. No industrial process in even the most sophisticated pharmacalogical facility in the world would be capable of carrying out the sophisticated and complex chemical reactions that our body does every day, silent and unseen.
Lets start by looking at the chemistry of fat. Essentially any animal or vegetable fat is a triglyceride, which is basically shaped like an E:
Three fatty acid chains are connected to a glycerol backbone, hence the name. Note that the 3 fatty acid chains are all straight, with the carbon atoms linked by single bonds. We call this a saturated fat because you can’t fit any more hydrogens on it.
Contrast that structure with this:
The third fatty acid chain has a double bond (in green). This molecule is no longer saturated, as there is room for two more hydrogens. That is, two hydrogens could be added across this bond, to convert it to a single bond and make it look like the molecule in the upper image. So because it is not saturated, we say it is unsaturated. Specifically, it is monounsaturated, as there is one double bond.
If there is more than one double bond, it is said to be polyunsaturated.
Now, you will note that the carbon chain with the double bond is bent. The implications of this is that the molecules will not stack together very well on top of each other, in just the same way that regular shaped boxes will stack together easier than irregular shaped boxes.
This means that monounsaturated triglycerides are generally liquid (like olive oil) and saturated fats (like lard) are solid at room temperature.