Macronutrients 101: Lipids

In the last post, I’ve explaied today’s most dreaded macronutrient- carbohydates. Now I’ll continue on talking about lipids or fats. Once feared and now promoted by “low-carb” fad diets, fat is simply another misunderstood macronutrient.

The true meaning of a lipid is something that is “hydrophobic” or is insoluble in water. Hence, not all fats are involved in energy production but have varying functions in the body. In essence, lipids can be broken down into three types:

1) Triglycerides or dietary fat

2) Phospholipids which form cellular membranes

3) Cholesterol which is present in animal cellular membranes or acts as a hormone, bile, and vitamin D precursor.

Where do lipids come from? Unfortunately it’s true, lipids are made from metabolic byproducts of glucose. However, it is important to note that glucose doesn’t magically turn into fat but EXCESS glucose does. Don’t you worry, fat cannot be converted into sugar or protein so if you eat excess fat it will simply remain as fat. 😉

Lets start with discussing dietary fat. Two major components of triglycerides are glycerol and fatty acids. Glycerol is a simple three carbon sugar to which three different fatty acids bind to. Fatty acids are long chains of carbon atoms bound to each other in a zig-zag pattern. It is important to note that a carbon atom is capable of forming a total of four bonds. In saturated fats, carbon atoms form one bond with each other while their other bonds form with hydrogen atoms.

Some fatty acids can have carbon atoms that form double bonds with each other which causes kinks in this zig-zag. These kinks prevent the fatty acids from being tightly packed and hence are called “unsaturated“. The number of double bonds in the fatty acid determines its degree of saturation. For example, if there is only 1 double bond than the fatty acid is “monounsaturated” but if it has multiple double bonds than it is called “polyunsaturated“. These double bonds effect the fat’s density making saturated fat be solid at room temperature (animal fat) and unsaturated fat be liquid (plant oil). Apart from the physical properties, the two types of fat are actually metabolized differently by our bodies and have different outcomes on our health.

Now you may be wondering what omega fatty acids are? They are simply a type of unsaturated fatty acids that have the double bond either 3 (omega-3) or 6 (omega-6) carbons away from their end. The catch is that our bodies can synthesize all sorts of fatty acids except for these omega fatty acids. Hence, we must obtain them from dietary sources like chia and flax seeds.

Now the term phospholipid might be something new for you. Phospholipids are the fats that make up the membranes of our cells and are comprised of two fatty acids and a phosphate group attached to a glycerol. The combination of all these molecules gives the phospholipid a unique property of having one half of the molecule be soluble in water and the other be insoluble. The cellular membrane than forms from two phospholipid layers. The fatty acid regions face each other and are insulated from water by the outward facing water soluble phosphate parts. These membranes are vital as they control the molecules that can enter or exit the cell.

As you can see, lipids are important macronutrients for our bodies. They make up our cellular membranes and are light efficient energy storages. It is important to note that our body can synthesize all lipids apart from omega acids from carbohydrates. This could explain why people living on high carb, low fat diets can still be healthy.

Hopefully that clears things up 😉 In the next post I’ll talk about something even more feared and even more misunderstood. Cholesterol! I know it’s not exactly a macronutrient but I think it’s important to talk about it 😉

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