Cholesterol and fat are not one substance, but fat contains cholesterol. Generally speaking, fat refers to the lipids in the human body, including glycerides, phospholipids, and small amounts of cholesterol, which are found in the subcutaneous tissues of humans and animals and have the function of storing, providing energy, and protecting organs. Fat is one of the essential nutrients, and too much or too little of it can cause discomfort or even illness. Cholesterol, as a class of chemicals, is found throughout the body. Biochemical tests can also measure the levels of HDL cholesterol and LDL cholesterol in the blood to screen the body for abnormalities. High levels of total cholesterol can lead to or indicate cardiovascular diseases such as atherosclerosis, hypertension, and primary hypercholesterolemia; low levels can lead to or indicate hyperthyroidism, anemia, and malnutrition.