You need fats — technically called lipids — to survive, in addition to other large molecules including carbohydrates, proteins, and nucleic acids. Yet, many people avoid fats in their diet.
Lipids are nonpolar molecules, which means their ends are not charged. Because they are nonpolar and water is polar, lipids are not soluble in water. That means the lipid molecules and water molecules do not bond or share electrons in any way. The lipids just float in the water without blending into it. You’ve probably heard the old adage, “oil and water don’t mix.” Well, oil is a liquid lipid. Butter and lard are examples of solid lipids.
Three major types of lipid molecules exist.
Phospholipids: These lipids are made up of two fatty acids and a phosphate group. These are the type of lipids used in the cell membranes of every cell in every animal. These lipids have structural functions. They aren’t the type that are floating around bloodstreams and clogging arteries.
Steroids: These lipids have four connecting carbon rings and a functional group that determines which steroid molecule it is. These lipid compounds generally create hormones. Cholesterol is a steroid molecule that is used to create hormones, such as testosterone and estrogen. So, for a healthy sex life and other important functions, you need cholesterol.
Cholesterol is transported around the body by other lipids. If you have too much cholesterol floating in your bloodstream, that means there is an excess of fats carrying it through your bloodstream, and that can cause trouble. The fats and cholesterol molecules can get stuck in your blood vessels, leading to blockages that cause heart attacks or strokes.
Triglycerides: Triglycerides are made up of three (tri-) fatty acid molecules and a glycerol molecule. These are the typical fat molecules. They are formed from an excess of glucose; after the liver stores all the glucose it can as glycogen, whatever is remaining is turned into triglycerides. The triglycerides float through your bloodstream on their way to be deposited into adipose tissue.
Adipose tissue is the soft, squishy, visible fat you can see on your body. Adipose tissue is made up of many, many molecules of fat. And, the more fat molecules that are added to the adipose tissue, the bigger the adipose tissue (and the place on your body that contains it) gets.
When you use up all your stored glucose (that doesn’t take long, sugars “burn” quickly in aerobic conditions), your body starts breaking down glycogen, which primarily is stored in liver and muscle. Liver glycogen stores can typically last 12 or more hours. After that, your body starts breaking down adipose tissue to retrieve some stored energy. That is why aerobic exercise (and enough exercise to use up more calories than you took in that day) is the best way to lose fat.
