Primary care physicians are especially good at reading situations that come up all the time. So far, not many people have taken on fasting as a health practice in the serious way that I have recommended on this blog. (See the fasting section in “Miles Kimball on Diet and Health: A Reader's Guide” for what I mean by taking fasting on seriously.) So the way cholesterol readings are affected by extended fasts are unfamiliar to most primary care folks.

Fasting for an extended period tends to raise cholesterol. Why? My intuition is that if you are burning body fat, doesn't it have to get to the cells somehow. That makes for more lipids in the blood, which a lipid panel will show up as more cholesterol.

In the article shown at the top of this post, “Hypercholesterolaemia of prolonged fasting and cholesterol lowering of re-feeding in lean human subjects.” K.G. Thampy reports the elevation of cholesterol after a week of fasting in his study of 36 lean, healthy adults. There is an important detail: In K.G. Thampy’s results, although cholesterol readings go up after one week of fasting, they go down after three weeks of fasting. Assuming this result replicates, this must come from something beyond my simple theory of transport of fat from body fat affect cholesterol readings. Somehow, after a three-week period, the body finds a way to get calories from body fat to the cells even with a low concentration of cholesterol in the blood. (I wonder how ketones are counted in a standard cholesterol test.)

Results from 36 individuals are worth more than from 1, but you might be interested in seeing my results.

Here are my standard cholesterol test results after 6 days of eating less than 500 calories a day (see “My Modified Fast.”):

Here are my standard cholesterol results after eating one big meal a day every day for several weeks:

These two tests were only a few weeks apart. In any case, my knowledge that an extended fast could give the illusion of a high-cholesterol problem came in handy in dealing with my doctor. He had suggested I get a test again 3 months later, which would have been less convenient. I insisted on doing the test at an earlier, more convenient time on the basis that the test results were affected by my having been in the middle of an extended partial fast.

In addition to educating my doctor about the effects of extended fasts on cholesterol readings in standard tests, I have been educating my doctor about the better cholesterol tests. Actually, I sent him the link to last week’s post “Standard Cholesterol Tests are Substandard; Better Cholesterol Tests are Available,” and he arranged for me to get the better type of cholesterol test. Here are the results from that test; you can see how much more detailed they are:

For organized links to other posts on diet and health, see:

• Miles Kimball on Diet and Health: A Reader's Guide