This week for the Back to Basics series we are getting into fat. Last week we covered part II of carbohydrates where we talked about good sources of carbs, how to avoid a energy crash, and correct portion sizes for carbs.
Fat, like carbs, are often misunderstood. So today I’m breaking down it all down for you sharing why they are important, how the body uses them, and how much we need for our bodies to function properly. Fats are often seen as “bad” because they are mainly associated with being the culprit of undesirable weight. And yes when we consume more calories than our body needs that is true, however, fats are tremendously essential to our bodies and our physical health. They are critical for our brain function, protecting our organs, controlling inflammation, along with many other functions that I'll go over in a bit.
WHAT ARE FATS?
Remember the macronutrients were the three main food groups that our bodies need every day: carbohydrates, fat, and protein. Fats contain about 9 calories per gram - twice the amount of calories of carbohydrates and protein, which contain 4 calories per gram. They are made up of glycerol (an alcohol) and three fatty acids, which are long carbon-hydrogen chains that end in a carboxyl group. There are two general types of fat: saturated and unsaturated.
SATURATED FATS (SOLID FAT) contain more hydrogen atoms making them more jam-packed and rigid in structure. These fatty acid molecules lay flat and stack tight against each other resulting a solid shape at room temperature (view image below). Saturated fats are often associated with cardiovascular disease because they tend to raise LDL (bad) cholesterol and lower HDL (good) cholesterol levels in the blood. Over time if eaten in excess these fats start to replace our cell walls with solid fat preventing nutrients from entering in. Solid fat also starts to harden parts of organs and line the arteries, which can block the flow of oxygen and nutrients in the body. You'll find saturated fats in in meat, coconut, and palm oils.
UNSATURATED FATS (OILS) have less hydrogen atoms attached creating a kink in their molecular structure. This prevents them from packing in and stacking on top of each other so they pass more fluidly throughout the body. This is what gives them their liquid characteristic at room temperature. Unsaturated fats are considered "healthy" because they provide your cells with the flexibility they need to allow nutrients in and flow nicely in the body. These would be oils like olive, vegetable, and grapeseed for example.
TRANS FATS (PARTIALLY HYDROGENATED) FATS are a type of unsaturated fat that rarely occur in foods naturally. What makes these stand out from the rest is that these fats have undergone a process of hydrogenation (hydrogen atoms are added) to extend their shelf-life. In this process, the oil is solidified. Manufactures created this process because saturated fats had become very unpopular by consumers. Unfortunately, because their physical properties are changed they act like solid fats do in the body raising LDL cholesterol levels and lowering HDL cholesterol levels resulting in a clogging of the arteries. Trans fats are typically found baked goods, margarine, and fried and processed foods.
HOW DOES OUR BODY USE FAT?
- Energy: carbohydrates are our body’s preferred source of energy but when it is unavailable fat is used as an alternative. Fat is not as easy to digest since it’s a more complex molecule reserving twice as many calories of carbohydrates or protein
- Structure: they make up most of the structure to many cell membranes which play an integral role in our body’s development
- Signal carrying: they play a part in cell-to-cell communication by conducting signals to other cells in the body
- Protection: they provide an extra layer of protection so that our organs are cushioned from jarring motions
- Insulation: they provide insulation for our organs and body to regulate body temperature and keep us warm
- Absorb Vitamins: they help us absorb fat-soluble vitamins: A, D, E, and K, all of which are essential for our daily diet. Vitamin A promotes good vision, vitamin D helps for the absorption of calcium, vitamin E is good for our protecting our cells, and vitamin K assists in blood clotting
- Brain: the brain uses glucose as it’s preferred source of energy, about 120 grams per day. When there is a lack of glucose the body will start to produce ketones from fat that will fuel your brain. Ketogenic diets are generally prescribed to those who suffer from epilepsy and seizures
- Fat cells: Any excess calories that are consumed that are not needed immediately for our body is stored in our fat cells
DIGESTION OF FATS
Digestion of fat begins in the mouth when the food is chewed an enzyme called lingual lipase begins to emulsify the fat with saliva. The food (bolus) continues to move down into the stomach where stomach acid starts to breakdown the fat into smaller pieces. Fat is held in the stomach as digestive enzymes and bile acids are being prepared to convert fat into something more absorbable in the body. This is why we stay full for longer period of time when we've consumed fat. You know how oil acts in water? The same thing happens in the body. Fat requires emulsification (mixing together) in order to be further digested and absorbed, but while the fat sits there it's being worked on by an enzyme called gastric lipase. Only a small amount of fat is digested in the stomach by this enzyme. Essentially, most fat digestion occurs in the small intestine. So as the stomach slowly releases fat globules (droplets) into the duodenum (the beginning of the small intestine) it comes into contact with bile acids that are released by the gall bladder. Bile acts like a detergent allowing the lipases (pancreatic and intestinal lipase) in the small intestine to digest the fat globules small enough so that they are able to pass through the lining (wall) of the intestine where they are absorbed and converted into chylomicrons. These chylomicrons are "fat packages" released into the lymphatic system eventually entering the blood circulation where they deposit their contents all throughout the body until they shrink into smaller empty packages and travel to the liver to be recycled. I'm hoping I didn't lose too many people. There's a lot more to it that I am open to discussing in a later post. Here for the 101 I want to give you the bare basics without overwhelming you (too much).
HOW MUCH DO I NEED?
Since everybody's bodies and lifestyles are different there is no one size fits all. With health status, activity-level, metabolism, genetics, and stress coming into play all of those will have to be calculated according to your goals. It’s best to talk to a registered dietitian so you can get a full dietary assessment and accurate energy intake requirement.
I really hope this 101 helped give you a better understanding of what fat is and how are body uses it. For part 2 of this I would like to help you apply this information: what are good sources of fats, what are the right portions, and how they affect carbohydrate digestion.
Please comment below if you have any questions or how you would like me to dig deeper into this. I would love to know what my readers would like to know about fats!