Numerous conditions can cause extremely high cholesterol levels in people with healthy lifestyles. According to Dicken Weatherby, a naturopathic physician and author of the book "Blood Chemistry and CBC Analysis," a diet high in carbohydrates, especially refined carbohydrates, starches and other fast-acting sugars, and hydrogenated fats is more likely to cause an increase in total cholesterol. Despite consuming a diet low in carbohydrates and hydrogenated fats, and despite regular physical exercise, cholesterol levels may be extremely high in some individuals.
Familial Hypercholesterolemia
Familial hypercholesterolemia can cause extremely high cholesterol levels in individuals with healthy lifestyles. According to the University of Maryland Medical Center, or UMMC, familial hypercholesterolemia, also known as Type II hyperlipoproteinemia, is an inherited condition -- a condition passed down through families -- in which a person has extremely high levels of low-density lipoprotein, or LDL, cholesterol at birth. LDL cholesterol is also known as bad cholesterol. The UMMC states that familial hypercholesterolemia can cause heart attacks at an early age. This condition is caused by a gene mutation on chromosome 19 that makes the body unable to remove LDL cholesterol from the bloodstream. Common signs and symptoms associated with familial hypercholesterolemia include fatty, cholesterol-rich skin deposits, cholesterol deposits in the eyelids and chest pain, or angina.
Primary Hypothyroidism
Primary hypothyroidism is a thyroid-related disorder that can cause extremely high cholesterol in people with healthy lifestyles. The Merck Manuals website states that primary hypothyroidism is a condition in which the thyroid gland does not produce sufficient amounts of certain important hormones. Hypothyroidism may be caused by autoimmune disease, treatment for hyperthyroidism, radiation therapy, thyroid surgery or certain medications. Although hypothyroidism can occur at any age, it's most commonly seen in the elderly, affecting 10 percent of women and 6 percent of men over the age of 65. Possible signs and symptoms associated with primary hypothyroidism include extremely high cholesterol, mental and physical sluggishness and, in severe cases, myxedema coma -- an uncommon yet potentially extreme manifestation of hypothyroidism.
Pregnancy
In some cases, pregnancy can cause extremely high cholesterol levels in people with healthy lifestyles. According to the American Pregnancy Association, or APA, there are numerous possible complications during pregnancy, including gestational diabetes, pregnancy-induced hypertension and urinary tract infections. Some women also experience extremely high cholesterol levels during pregnancy. Uncontrolled cholesterol during pregnancy may be due to the effects of elevated levels of estrogen and progesterone on the liver. In most cases, cholesterol levels return to normal after delivery, and especially after breastfeeding begins. The long-term risk of heart disease from uncontrolled cholesterol levels for nine or 10 months is believed to be relatively minimal, although this has not been confirmed by scientific studies. Cholesterol levels among pregnant women are usually at their highest during the third trimester.
