The pathological conditions in which there are high levels of fats in the blood. The medical term for these conditions is hyperlipidemia, which is made of three parts; hyper-, is a prefix meanings more or extra, lipid is fat, and emia is a suffix indicating that the condition is in the blood. Hyperlipidemia is a general term, it could be either high cholesterol in the blood (hypercholesterolemia), high triglycerides in the blood (hypertriglyceridemia) or it could be both.
When we talk about too much cholesterol in the bloods we mean by that high LDL (the bad cholesterol), there is nothing called too much of a good thing; so high levels of HDL (the good cholesterol) is not considered a disease. We have to remember that the absolute values of these two lipoproteins are not that important but rather the ratio between the two. So lower than normal value of HDL, even in the presence of normal value of LDL, is still considered hypercholesterolemia.
Hereditary
Many factors can lead to having high lipid levels in the bloods like defected copy of one of the several genes that participate in lipid metabolism. The mutation might cause more production of LDL or decrease its rate of clearance from the blood. On the other hand, the mutated gene might promote faster HDL clearance or lower its production. Either way, the balance between the good cholesterol and the bad cholesterol is disturbed and there is more of the bad stuff in the blood. In such hereditary cases, a positive family history is always present, and these individuals develop arteriosclerosis earlier than usual.
Food habit
The majority of the cases are not caused by hereditary factors, but rather secondary to other conditions. Obesity is considered a risk factor because it usually indicates a certain life style with high food consumption and low physical exercises, both are incriminated in high blood lipids. High consumption of food rich in saturated fat such as found in meats, non-skim dairy products, butter and some artificially hydrogenated vegetable oils is particularly risky. We have to remember that high intake of cholesterol prevents the uptake of cholesterol circulating in the blood by the liver, and these kinds of food are not short of it.
Diabetes
Diabetes mellitus, especially if poorly controlled, is a major contributor to high blood lipids. Other diseases such as kidney failure or hyperthyroidism may also cause hyperlipidemia. Drugs such as estrogens, oral contraceptives, and corticosteroids can increase the blood lipid level as well. The high levels of triglycerides are caused by similar factors that lead to high LDL, but there is no established link between high triglycerides and cardiovascular diseases. The consumption of a high calorie diet and excessive use of alcohol are also contributing factors to high blood levels of triglycerides.