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The term "fat" has really gotten a bad rap in recent years. We even turned it into a slang adjective to describe someone who's overweight. Well, it's supposed to be a noun!
Dietary fat (a.k.a fatty acids) are chemical compounds that store more than twice the energy of carbohydrates and proteins. In fact, one gram of fat provides 9 calories while one gram of carbohydrates or proteins only provides about 4 calories. This is why fat storage is so important for humans, especially back in prehistoric times - we're able to go for long periods without food. We can survive for months on the fat we've stored!
Storing a lot of fat isn't really a good thing in today's society. After all, most of us eat more than one meal per week. So what should we do? Eat a balanced diet with enough fats to keep you healthy!
The consensus has been that the average diet is far too rich in calories, fats and cholesterol. Due to their correlation with heart disease and cancer, it has understandably become a great concern in society.
The problem is that most people also don't understand what fats are to begin with. Wouldn't it be nice to make your own decisions about what you eat?
There are tons of resources on the internet, in magazines and through other media outlets that claim to have the "secrets" to rid yourself of these "bad" things. Many of the fad diets and magic diet pills are potentially dangerous and unhealthy.
The best way to get yourself into better shape is to start eating a balanced diet. Understanding what fats are and how they are used is a good first step in the process!
The importance of fats have been overshadowed by the dark cloud of cancer and cardiovascular disease hovering over them. They're required for healthy living! Here are some of the major functions of fat:
2) Cell membranes
3) Lubrication of joints
4) Slows digestion of food (feel full for longer!)
5) Aid in the absorption of the fat-soluble vitamins (A, D, E, K)
6) Makes food taste good! Yummmmmm...
You like tasty food, right? Don't we all? This is what makes eating so enjoyable! It's another one of those adaptations humans have made up to make sure we're getting enough fats in our diet to survive long bouts without food.
But in today's society, as you know, eating too many fatty foods can also wreak havoc on your health. Don't worry, there's hope...eat more good fats than bad fats! Here's some information on saturated and unsaturated fats.Top of Page
Dietary fat is used to make steroid hormones (these are good!), cholesterol and many other vital compounds required for healthy living. As this statement implies, there're tons of functions of dietary fats that happen behind the scenes. Here're some of them...
They're used to make the insulation wrapping nerves called myelin sheaths. Without this, most of the nerves in your body simply would not conduct a signal too and from the brain.
They form the structure of each and every cell membrane inside your body. In short, they're composed of lipid (meaning fat or, in the liquid form, oil) bilayers with inserted proteins and cholesterol molecules. This layout regulates what can enter and exit the cell. So, if you have no lipid membranes, you have no cells!
They're used to lubricate your joints.
They're used to make the hormones, or little messenger molecules that travel long distances to regulate normal bodily functions. Most functions of the body require the action of some sort of hormone which often made from dietary fat.
That stuff happens behind the scenes. But, what about the fat in your belly or legs? What does that do?
They're shock-absorbing! In other words, if you sat in a chair all day with no fat in your butt, you would end up putting huge amounts of stress on your pelvis and spine.
Storage of dietary fat reduces heat loss like the fatty blubber of a seal. It keeps you warm when it's cold outside! This one is obviously less significant in this day and age.
Energy! The fat you see on your body is known as adipose tissue. This is where fats are removed from storage to be used for energy.
Let's think about the energy concept a little more...Top of Page
This is actually a tough job for your body since dietary fat (or oil) doesn't mix with water. In other words, the fat will simply float or tend to "exclude" water from itself. The result is that you'll have "clumps" of fat in your stomach and your intestine. This very concept makes it difficult for water-soluble lipases (enzymes that break down fat) to act on the dietary fat you've ingested. The enzyme simply can't get near the fat!
You may have heard the idea that fats take longer to digest than carbs and proteins...well, here's your reason why! It takes time for digestion to occur because dietary fat is simply difficult to digest with water-soluble enzymes. Fats also make you feel full or satisfied for longer because of the time required for digestion to occur.
As fats are emulsified (or squished and mixed by the stomach) and forced into the small intestine, a hormone known as CCK (short for cholecystekinin) is released from the pancreas, signaling the gallbladder to secrete bile. Thank goodness for this.
Bile is a complex molecule that increases the water solubility of dietary fats. It does this by attaching to the outer edge of the fat "glob" that's accumulated in the intestine. Portions of the bile molecules are charged, thereby allowing the glob of fat to interact with water. Lipases can now act on the fat!
You may be familiar with a molecule known as Taurine present in several kinds of energy drinks - this is actually the point where Taurine acts. Basically, bile is made of cholesterol (which is made from dietary fat!) with the attachment of charged amino acids. One of these amino acids is Taurine which substantially increases the solubility of fat globules so that water-soluble lipases can break down the fats in the intestine (the other amino acid used for this purpose is Glycine). On the other hand, Taurine is also a caffeine "accelerant", as they say.
Lipases break down the dietary fat into smaller molecules of glycerol and free fatty acids (or single chains of fats). At this point, the fats can be stored in adipose tissue (your butt!) immediately used for energy or used to make specialized lipoproteins.Top of Page
As a general rule, your body prefers to use the chemical pathway followed by glucose to create energy. With this in mind, your body will always use carbohydrates and simple sugars for energy before it starts dipping in to any sort of fat storage. It's just easier! It actually takes quite a bit more time and energy to break down fat storages for energy.
So when do you use fat for energy? That's right, when you don't have any more sugars or carbs to burn! When your liver and muscle glycogen storages (carbohydrate storage) are depleted along with available glucose, your body will then start to harvest the energy stored in fats. This sort of situation usually occurs during long bouts of exercise or fasting (such as sleeping 8 hours at night!).Top of Page
Utilizing fats for energy is part of a complex, hormone-regulated system...
You know when you haven't eaten for a while and you start to get the jitters? Well, that's adrenaline (epinephrine)! This circulating adrenaline is what signals fats to be released from storage to be sent to energy-needing tissues. These fats are then broken down into a molecule called acetyl-CoA which is harvested for energy through the same pathway that glucose follows.
Here's a more thorough, complete (and more complicated) discussion of how fats are mobilized from storage and broken down for energy...(please skip if TMI!)
To begin with, there's an enzyme in your fat cells called hormone-sensitive lipase that reacts to the presence of epinephrine (street name: adrenaline) or glucagon (a hormone that acts in opposition to insulin). After this interaction occurs, a cyclic-AMP reaction cascade occurs, ultimately resulting in the release of free fatty acids and glycerol (this is the backbone of triacylglycerols, the storage form of fats) from the fat cell. The free glycerol is transported to the liver and chemically converted into a precursor molecule for glycolysis (the same pathway that harnesses the energy contained in glucose).
What about the fatty acids? The fatty acids attach to transport proteins called albumin in the blood and are taken to the tissues where energy is needed. Because fatty acids are, well, fat-soluble, they can pass right through the lipid bilayer of all cell membranes. In other words, it can enter directly into the energy-needing cell through its cell membrane.
Once the fatty acid is inside the cell, it's transported into the mitochondria through the use of coenzyme A and a fatty acid transport protein known as carnitine. Fatty acids are broken down into bunches of small molecules called acetyl-CoA in a process known as beta-oxidation. This number of molecules corresponds to half the number of carbons present in the fatty acid. So, if a fatty acid is 18 carbons long, you'll end up with 9 acetyl-CoA molecules. The basic idea remains the same for saturated, unsaturated and odd-numbered fatty acids with a few variations.
The acetyl-CoA produced by beta-oxidation can be directly inserted into the reaction sequence called the citric acid cycle (a.k.a TCA cycle or the Krebs cycle) from which many ATP molecules are derived. ATP is the energy source for all your bodily functions!
Are you eating the exact right amount of fat that you need? This is like trying to perfect your golf swing. It's extremely difficult! It's a very delicate system. But don't worry, you don't have to be perfect, just educated!
What happens when you get too much fat too often? Heart disease, certain cancers, diabetes and, more often than not, obesity. Doesn't sound too good, does it?
Too little fat and you'll end up deficient of all the fat-soluble vitamins, your nerve conduction will be slow, and children will have problems growing. That doesn't sound too good either.
So how much fat is enough? I like to use the 50/30/20 rule; that's 50% of your calories from carbs, 30% of your calories from proteins and 20% of your calories from fats. Strive to achieve this, along with getting enough exercise (try starting your own strength training program!) , and you'll be well on your way to living a long, healthy life. (The 50/30/20 idea is explained in more detail on the eating healthy page and a question submitted by one of your fellow readers!)
Let's try the 2,000 calorie diet example. The 50/30/20 rule dictates that 1,000 calories will come from carbohydrates, 600 calories from proteins and 400 calories from fats. Let's avoid any misunderstanding: this does not mean that 20% of what you eat is fat. Remember, 20% of your total calories should come from fat.
It's also allowable to increase this number to 30% (thereby lowering the calories taken from carbs or proteins by 10%) if you feel more comfortable and happy this way. It's probably just as good - just remember to get your exercise!
This sort of dietary guideline is meant for adults or older adolescents only. The fact is that growing children need more fats than to promote growth and development of the nervous system. Why do you think women naturally produce high-fat milk? This is because young children and infants need lots of fat to keep growing!
Before starting any such diet, be sure to check with your doctor to make sure that you're physically capable of pulling it off!Top of Page
As you're probably aware, there are different kinds of fatty acids - some of these we can create on our own (using an enzyme called fatty acid synthase) and others we must obtain from the diet.
So here there are, linoleic acid, linolenic acid and arachidonic acid are the essential fatty acids that you must get from your diet. Because linolenic acid and arachidonic acid can be made from linoleic acid, they're only essential when linoleic acid is limiting.
Was that a good tongue twister? The fact is that it doesn't matter: each one of these fats are present in many foods, so it's not really anything for you to worry about (as long as your eating a minimal amount of saturated fat per day).
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Water Soluble Vitamins
Fat Soluble Vitamins
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