You Might Not Have to Fast After All

Usually when your doctor wants to check your cholesterol scores, the blood is drawn first thing in the morning so that you will have not eaten for at least 8 hours beforehand (the "fasting state"). Why? One reason is the increase in triglyceride levels that is measured during a fat tolerance test. Another has to do with the way that the LDL score is calculated using the triglyceride score.

Yet the fasting state is by definition unusual: we don't usually go for more than 8 hours without eating. Except, of course, early in the morning. Researchers in Denmark wondered, justifiably, if cholesterol scores taken in the non-fasting state wouldn't be just as useful. After all, they'd represent our cholesterol scores the way they are more of the time (as well as being much more conveniently tested for all concerned)(Circulation 2008;118(20):2047-2056).

In addition to the administering usual health and lifestyle questionnaires, the researchers obtained the cholesterol scores of nearly 35,000 people. At the time of the blood draw, the participant was asked how long it had been their last meal. The time of day that the blood was drawn was also noted.

This information allowed the researchers to assess whether the specific cholesterol scores (LDL cholesterol, HDL cholesterol, total scores, triglycerides, and more) tended to go up after eating, down, or if they tended to stay the same.

The medical records of a subset of this group of people were followed for 14 years. The non-fasting cholesterol scores of those persons who experienced heart attacks or other cardiovascular problems were compared to the scores of those who did not have heart problems.

Interestingly, the researchers discovered that the difference between fasting cholesterol scores and non-fasting cholesterol scores was actually minimal. HDL and LDL cholesterols were actually slightly higher in the fasting state, while total cholesterol was basically the same and triglycerides were lower. Further, those non-fasting cholesterol scores could predict later health problems just as usefully as fasting scores.

What this means for you

This study challenges the prevailing belief that cholesterol scores obtained after not eating for 8 hours are the most accurate or useful. While it may take a while for people to stop requiring you to fast before your blood test, it will certainly make your life easier - which is always good news.

First posted: December 10, 2008