How Fat Works Inside Your Body – Part One

Fat. Most people think it’s delicious. It helps to enhance flavor (drumsticks or wings wouldn’t be the same without it). It’s bad for you. It’s also definitely good for you. But what exactly does it do? And what fat is “good” fat and what fat is “bad” fat? YLB is going to be starting a series discussing fat. We’re going to be taking a look at it and we’ll and breaking it down in to several different components. First we’ll be starting with the basics; we’ll do a brief breakdown of fat and discuss the most common terms associated with fat. We’ll also talk about fat metabolism and how it’s packaged up in your body. Then we’ll move on to oils and how it pertains to your food and cooking. There’s also a significant amount of debate on how toxic saturated fat can be to your arteries given specific diet modifications so we’ll be discussing that throughout the series as well. Let’s begin with a little intro…

What is fat?
If you didn’t already know, there’s more to fat than just fat. It’s encompassing several different factors with a few different main categories such as triglycerides, saturated fat, unsaturated fat, trans fat (or hydrogenated fat), and cholesterol. Let’s break them down one by one.

Triglycerides:
From time to time you may have come across the term triglyceride. All this word essentially means is the storage form of fat [3]. It contains a binding group with three fatty acid chains attached to it. All you need to do here is picture a flagpole with three flags attached to it. The flagpole is the backbone of the fat and the three flags are the fatty acids extending off of it. Whenever you eat fat your body digests a triglyceride and breaks down each fatty acid one by one before repackaging it as it’s own flagpole inside your own body. That flagpole of your fat then moves to where it’s needed inside your body. High fat intake in your diet is usually associated with high triglyceride levels in blood tests. So what are those fatty acids that rest on that flagpole? Read on.

Saturated fat:
Saturated fat is one type of fatty acid that sits on that flagpole. Generally speaking saturated fat is mostly found in animal foods. Ever notice that white stuff on your steak after it cools off? That’s saturated fat. Saturated fat is thought of as what’s generally solid at room temperature – which it’s why it is still thought this was the stuff that stuck to your artery walls (we’ll talk more about that later because it’s more complicated than just that). According to Up To Date (an evidence based, physician led resource), saturated fats are responsible for raising your total blood cholesterol. In addition to that, studies have shown that the saturated fats found primarily in red meats and dairy products are the ones most likely to increase your blood cholesterol [1]. So if you’re a milk drinker trying to lower your cholesterol levels you might want to think of going skim – or have less rocky road ice cream. We’ll talk more about why saturated fat raises blood cholesterol when we hit on LDL further down.

Unsaturated fat: The difference between saturated and unsaturated fat lies in the chemical makeup. A slight variation in the chemistry allows unsaturated fat to have a lower melting point so that causes it to generally be a liquid at room temperature [3]. These fatty acids would be be your oils (olive oil, coconut oil, avocado oil, etc) or fish oils such as omega-3. Unsaturated fats are primarily from plant and fish sources. According to the National Institute of Health, unsaturated fats can help to decrease your LDL cholesterol levels [2]. However, some newer research has questioned some benefits that unsaturated fats have. The National Lipid Association recently reviewed all research associated with unsaturated fat and they still do suggest as does the National Institute of Health that unsaturated fatty acids can help to reduce LDL levels [2,6].

One important takeaway from these two fatty acids is that most foods contain a variety of saturated and unsaturated fatty acids [3]. This is why it’s important to know what you are eating.

What about trans fat?
Trans fat is found primarily in deep fried foods and snack foods like cookies and crackers or even margarine and shortening. Trans fat results from a form of food processing where the chemistry of an unsaturated fat has been altered. For those unfamiliar with the process it essentially goes like this: hydrogen is added to the chemical make up of the unsaturated fat by bubbling hydrogen gas under pressure into liquid vegetable oils. The end product resembles something closer to saturated fat [3]. Stick away from this type of fat as an excessive amount of this fat can pose a significant health risk to your heart and brain [3]. Trans fat can lower HDL and and increase LDL levels and also trigger the body’s inflammation response [4].

History of trans fat?
When it comes to processed foods, nothing makes food better like solid fats. However, the food industry knows that oils just don’t make the same kinds of food that solid fats make. The food industry also had one other problem: preventing fats from going rancid. The hydrogenation process of unsaturated fats prolongs shelf life by changing the chemical structure to make it less susceptible to oxidization [4].

Cholesterol:
Cholesterol falls in another classification of fat. It’s not necessarily a fatty acid because it doesn’t attach to form a triglyceride but it’s still a fat [3]. Cholesterol is actually really important for many body functions (I’ll have to go more in depth about cholesterol at another time), so it IS actually important to get cholesterol into your your diet. Although there are more than just two forms of cholesterol, the two we’re going to focus on now are HDL and LDL, simply because they are the most commonly talked about types of cholesterol. In actuality, they’re a form of lipoproteins (cholesterol, protein, fat, and phosphorous) that help to package up fat in your body to where it’s needed most (cells, hormones, and if you have any left over – your waistline or arteries) [3].

LDL
All this stands for is low-density-lipoprotein. It essentially carries cholesterol made by the liver and from other sources and carries that cholesterol into your blood stream where it can be used by your cells to be made into things like certain hormones or cell membranes. The liver is responsible for helping to remove LDL from your blood stream after the LDL has taken it’s contents to where it’s needed but this is where it gets a little tricky – a diet high in saturated fatty acids increase the amount of cholesterol in the liver. According to the Harvard Medical School, the saturated fats taken in through diet increase LDL in the blood stream and the liver essentially gets backed up and can’t do it’s job of getting LDL from the blood stream back to the liver fast enough. What happens is LDL gets stuck in places it shouldn’t be, like your arteries [5]. If LDL wanders around the blood stream long enough it can become damaged through oxidization. The damaged LDL triggers a secondary removal process in your body that causes white blood cells to go out and “eat” this damaged LDL. These white blood cells bury themselves in your blood vessels where they digest the oxidized LDL and generally prevent it from reentering the bloodstream. The problem is that if your LDL remains high, it causes plaque to build up [3]. Your heat and brain don’t like that very much and this is where down the road, cardiovascular disease can develop. Enter HDL…

HDL
This stands for high-density-lipoprotein. HDL is responsible for cholesterol removal from cells and helps to excrete it from the body. It’s also naturally produced in the liver just like LDL is but in addition to that it’s also produced in your intestines. HDL works directly the opposite of LDL. HDL helps to transport cholesterol from random sources in your body and in your blood stream back to the liver to be excreted. In addition to being a transport HDL also has an antioxidant property which helps to keep LDL from becoming damaged in your vessels. Less oxidization = less potential of cholesterol and plaque formation in your blood vessels [3]. And that’s a good thing!

Now that we’ve told you about the most common fat terms, in part two we’ll be talking about the omega fats and we’ll continue to talk about what happens once fat is actually is inside your body and how it contributes to your waistline. The important take away from this post should be a couple of things: stay away from processed foods as they contain trans fat, keep a look out for foods that have a HDL component of cholesterol and include them in your diet, and a diet naturally high in triglycerides, saturated fat, and LDL can be contributors to cardiovascular disease.

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Sources:

1. http://www.uptodate.com/contents/dietary-fat?source=search_result&search=saturated+fat&selectedTitle=1%7E75
2. http://www.nlm.nih.gov/medlineplus/ency/patientinstructions/000104.htm
3. Hampl, Jeffry S. Wardlaw, Gordon, M. Perspectives in Nutrition. 7th ed. New York: McGraw-Hill Companies Inc., 2007. 8-9, 193-194, 199-200, 203, 207-211, 220-222. Print.
4. Boyer, Rodney. Concepts in Biochemistry. 3rd ed. New Jersey: John Wiley & Sons. 2006. 238, 246. Print
5. http://www.health.harvard.edu/newsweek/Understanding_Cholesterol.htm
6. http://www.lipid.org/sites/default/files/22-reeves_02_27_13.pdf