Triglycerides are an oily kind of fat made from carbohydrates. Like cholesterol they are not soluble in water or blood. They are carried on lipoproteins, VLDLs, Very Low Density Lipoproteins.
 

What are triglycerides used for?
Triglycerides are free fatty acids. They store a lot of energy. Just as we use oil for energy in furaces or vehicles, the body uses oil for energy.
Sugar is our "instant fix" for energy. Cells such as muscle cells can make energy almost immediately from sugar.
A long distance runner will burn sugar for the first five or seven minutes of the race. Then the muscles will be low in sugar and the blood will not be able to re-supply fast enough. The muscles start to use glycogen for energy. Glycogen is sugars joined together like pearls on a string. The muscles cells pop them off one at a time for energy. Glycogen is stored in muscles and in the liver. When the glycogen runs low, after twelve or fifteen minutes, the muscles start to burn fat as the major source of energy. The fat they use includes triglycerides.
EXERCISE BURNS TRIGLYCERIDES
 

Causes of high triglycerides (hyper-triglyceridemia)
Any disorder of carbohydrate will have an effect on triglycerides. Diabetics make more triglycerides.
Alcoholics take in excess carbohydrate in the form of alcohol, and the liver is less able to metabolise them.
Liver disease from any cause will elevate triglycerides.
Hypothyroidism (underactive thyroid) slows down everything including the metabolism of sugar. Underactive thyroid causes hyper-triglyceridemia.
 

How do triglycerides cause harm?
Triglycerides damage the liver, disrupting cholesterol metabolism. It is not as easy for the liver to break down triglycedrides. However the greatest damage done by triglycerides is to arteries. They are corrosive on arteries and allow cholesterol to be deposited in the arteries.