HDL and LDL are two different types of cholesterol that are measured as an index of a patient's risk for cardiovascular disease. HDL stands for high-density lipoprotein and LDL stands for low-density lipoprotein. Total cholesterol measures the combination of HDL, LDL and VLDL.
LDL is the cholesterol type most commonly thought of as a strong risk factor for atherosclerosis and heart disease. Oxidized LDL and the fraction called Lp-a produce a greater risk. Since HDL cholesterol reduces the risk, low HDL levels are not desirable.
The May 2004 Annals of Internal Medicine study showed that a third of Atkins Dieters suffered a significant increase in LDL cholesterol. One person's LDL shot from an unhealthy 184 to a positively frightening 283 (which means their total cholesterol was probably somewhere over 350). [Annals of Internal Medicine 140 (2004): p.769] With so many people on these diets, that could mean Atkins is endangering the health of millions of Americans. LDL cholesterol is, after all, one of the most important risk factors for the number one killer in the United States for both men and women: heart disease. [Circulation 89(1994):1329]