Fasting and cholesterol

How can you lower cholesterol without medications? And what happens to your cholesterol if you do intermittent fasting?
High cholesterol is considered a treatable risk factor for cardiovascular diseases such as heart attacks and strokes. There are many nuances to cholesterol which I do not want to get into, but traditionally, the main division has been between Low Density Lipoprotein (LDL) or ‘bad’ cholesterol, and High Density Lipoprotein (HDL) or ‘good’ cholesterol — although those are grossly oversimplified.
We also measure triglycerides, a type of fat found in the blood. Fat is stored in fat cells as triglycerides, but also floats around freely in the body. For example, during fasting, triglycerides get broken down into free fatty acids and glycerol. Those free fatty acids are used for energy by most of the body. So triglycerides are a form of stored energy. Cholesterol is not. This substance is used in cellular repair (in cell walls) and also used for to make certain hormones.
The Framingham Heart studies of the early 1960s established that high blood cholesterol levels as well as high triglycerides are associated with heart disease. This association is much weaker than most people imagine, but results were slightly improved when LDL was considered separately from HDL. Since cholesterol is found at the site of atheromatous plaques, the blockages in the heart, it seemed intuitive that high blood levels plays a role in ‘clogging up the arteries’.
The question, therefore, became, what causes high blood levels of cholesterol? The first thought was that high dietary intake of cholesterol would lead to high blood levels. This was disproven decades ago. One might (mistakenly) think that decreasing dietary cholesterol may reduce blood cholesterol levels. However, 80% of the cholesterol in our blood is generated by the liver, so reducing dietary cholesterol is quite unsuccessful.
Studies going back to Ancel Key’s original Seven Country Studies show that how much cholesterol we eat has very little to do with how much cholesterol is in the blood. Whatever else he got wrong, he got this right – eating cholesterol does not raise blood cholesterol. Every single study done since the 1960s has shown this fact repeatedly. Eating more cholesterol does not raise blood levels.
So, if dietary cholesterol didn’t raise blood cholesterol, what did?
Low-fat diets and cholesterol
The next thought was that lowering dietary fat, especially saturated fats, may help lower cholesterol. Yet there is plenty of evidence to the contrary. In the 1960’s the Framingham Diet Study was set up to specifically look for a connection between dietary fat and blood cholesterol levels. This was the same Framingham as the famous Heart Studies, but references to the Framingham Diet study are virtually non-existent. Why haven’t you heard of it, before? Well, the findings of this study showed no correlation between dietary fat and cholesterol levels whatsoever. Because these results clashed with the prevailing ‘wisdom’ of the time, they were never published in a journal.
In some studies, extremely low-fat diets can lower the LDL slightly, but they also tend to lower the HDL so it is arguable whether overall health is improved. Other studies show no such lowering. For example, here’s a study in 1995, where 50 subjects were fed either a 22% or a 39% fat diet. Baseline cholesterol was 173 mg/dl. After 50 days of a low fat diet, it plummeted to… 173 mg/dl. Oh. High-fat diets don’t raise cholesterol much either. After 50 days of high fat diets, cholesterol increased marginally to 177 mg/dl.
Whenever somebody is told their cholesterol is high, they say “I don’t understand. I’ve cut out all fatty foods”. Well, reducing dietary fat will not automatically change your cholesterol. Some may see significant changes, but for most there are marginal changes at best. So, what to do?
“A little starvation can really do more for the average sick man than can the best medicines and the best doctors” – Mark Twain
Studies show that fasting is a simple dietary strategy that can significantly lower cholesterol levels.
Now, there are many controversies about lipids that I do not wish to get quagmired in. For example, there are many details about particle size and calculations of total particle numbers and newer particles etc. that are beyond the scope of this discussion. I will limit this discussion to the classic HDL/ LDL/ and triglycerides.
HDL
The lower the HDL, the higher the risk of CV disease. This association is actually much more powerful than that for LDL, so let’s start here.
Several years ago, Pfizer poured billions of dollars into researching a drug called torcetrapib (a CETP inhibitor). This drug had the ability to significantly increase HDL levels. If low HDL caused heart attacks, then this drug could save lives. Pfizer was so sure of itself, it spent billions of dollars trying to prove the drug effective.
The studies were done. And the results were breathtaking. Breathtakingly bad, that is. The drug increased death rate by 25%. Several more drugs of the same class were tested and had similar effects. Just one more illustration of the ‘Correlation is not Causation’ truth.
Nevertheless, we care about HDL because it is a marker of disease, just as a fever is often the visible sign of an underlying infection. If HDL is decreased, then it may be a clue that the underlying situation is also worsening. What happens to HDL during fasting? You can see from the graph that 70 days of alternate daily fasting had a minimal impact on HDL levels. There was some decrease in HDL but it was minimal.
Triglycerides
The story of triglycerides (TG) is similar, although there is likely more evidence that elevated triglycerides are more strongly associated with heart disease risk.
What happens to TG during fasting? There’s a 30% decrease in TG levels (good) during alternate daily fasting. In fact, triglyceride levels are quite sensitive to diet. But it is not reducing dietary fat or cholesterol that helps. Instead, reducing carbohydrates seems to be the main factor that reduces TG levels.
LDL
The LDL story is much more contentious. Statin drugs lower LDL cholesterol quite powerfully, and also reduce CV disease in high risk patients. But these drugs have other effects, often called the pleiotropic (affecting multiple systems) effects. For example, statins also reduce inflammation, as shown by the reduction in hsCRP, an inflammatory marker. So, is it the cholesterol lowering or the pleiotropic effects that are responsible for the benefits?
This is a good question to which I do not have an answer yet. The way to tell would be to lower LDL using another drug and see if there are similar CV benefits. The drug ezetimibe in the IMPROVE-IT trial also had some CV benefits, but they were extremely weak. To be fair, the LDL lowering was also quite modest.
What happens to LDL levels during fasting? Well, they go down. A lot. Over the 70 days of alternate daily fasting, there was about a 25% reduction in LDL. To be sure, drugs can reduce them by about 50% or more, but this simple dietary measure has almost half the power of one of the most powerful classes of medications in use today.
But why does fasting work where regular diets fail? Simply put, during fasting, the body switches from burning sugar to burning fat for energy. Free fatty acids (FFA) are oxidized for energy and FFA synthesis is reduced (body is burning fat and not making it). The decrease in triacylglycerol synthesis results in a decrease in VLDL (Very Low Density Lipoprotein) secretion from the liver which results in lowered LDL.
One way to lower LDL is to make your body burn it off. The mistake of the low-fat diet is this – feeding your body sugar instead of fat does not make the body burn fat – it only makes it burn sugar. The mistake of the Low-Carb, High-Fat diet is this – giving your body lots of fat makes it burn fat, but it will burn what’s coming into the system (dietary fat). It won’t pull the fat out of the body.
Here’s the bottom line for those big-picture, spare-me-the-details kind of folks. Fasting has the following effects:
- Reduces weight
- Maintains lean mass
- Decreases waist size
- Minimal change in HDL
- Dramatic reductions in TG
- Dramatic reductions in LDL
That’s all good. Whether this will all translate into improved cardiac outcomes, I don’t have the answer for you. My guess is Yes.
That’s why I use fasting as a tool to help my patients improve their cardiovascular risk.
—
Jason Fung
More
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His book The Obesity Code is available on Amazon.
His new book, The Complete Guide to Fasting is also available on Amazon.
Thanks for your publication.
Im 32 years old and I have been Fasting for about 1 year. I eat only vegetable which grows above the ground, eat dairy products (real ones), cook with coconut oil or butter and the only high glycemic food I eat is on the breakfast (1 small banana). I love avocado, nuts and seeds...not all seeds.
I read your publication and I am said because for me it didn't work well...Is not a matter about weight loss because I am a big sportive with around 11 hours of training per week. I do endurance sports it is why I am very interested in Fasting diet...
In my last results of blood sample my total cholesterol rise a lot...almost the double if I compare with the last year blood sample exams and my LDL is quite high too...above the limits for people with my age. That's true that my HDL raised a lot and my Tryglicerides decreased too.
What is for you the normal values of HDL, LDL, TOTAL and tryglicerides in a blood sample? Or the ratio between them?
Thanks a lot
Serge
http://www.ti.ubc.ca/2014/05/30/higher-potency-statins-and-the-risk-o...
Steve thank you for this very well-researched report. Best of luck.
If you are a member you can direct a question to Dr Fung here:
https://www.dietdoctor.com/member/ask-the-experts
http://cholesterolcode.com/the-fasting-disaster/
I just ran an experiment where I only consumed Water/Coffee/Daily Multivitamin/Electrolyte Supplement (Noncaloric, Na, K, Mag, Ca, etc) for 7 Days.
My Labs on the 7th day
Cholesterol 147 -> 228
HDL 46 -> 40
LDL Calculated 90 -> 162
Triglycerides 53 -> 128
Average Daily
Glucose Readings 60-80
Ketones 1.5 - 2.5
I've been practicing intermittent fasting (16:8) and omad (one meal a day) for 75% of the last 8 months or so, implementing a High Fat, Low Carb diet most of the time as well, prior to the fast.
My interpretation of my results
Elevated Cholesterol: With Cholesterol being such an agent of healing and hormone creation, I think my body had upper range of it due to possible increased steroid hormone production and possible increased cell membrane repair.
Decreased HDL: HDL to my understanding takes cholesterol from the blood stream to the liver to be processed to make bile. If I'm not ingesting anything, then I'd expect this value to decrease because of the decrease in need to make bile.
Increased LDL: I've been learning of the many variations of LDL, and how they are water soluble making them essential to transport triglycerides and cholesterol. So I'd expect on increase in this due to fat being the main source of fuel circulating in my blood stream.
Increased Triglycerides: Ketone production to my understanding needs free fatty acids to be converted into ketones. I assume that an elevated level of triglycerides is due to the demand to make ketones (barring the triglycerides are readily broken down to a glycerol and 3 free fatty acids for ketogenesis and gluconeogenesis).
I've listened to many different theories of normal lab values shifting to a new normal when on a Ketogenic Diet. For when you use fat as energy and increase cholesterol and saturated fat intake, while restricting carbohydrates, your body can respond differently but still in a healthy way.
I was wondering if anyone has come across anything like this and have their own explanation? Thank you!
Maika
My cardiologist kept saying no to niaspan because this study showed it didn't reduce events. After a few years, I got curious and went and looked up the study, and it turns out that both the control and experimental group were on statins. So niaspan doesn't reduce events *over* a statin, but it's likely you could've done the reverse experiment and proved statins didn't reduce events over niaspan.
Course the NNT isn't great for statins anyway.
My triglycerides have improved after 3 months of fasting and ridiculously big salads (RBSs), but are still bad. I'm vaguely considering going back on niaspan; my hesitation is just that the pills are so damned big, it's irritating.
But I fully expect them to drop further as I continue the fasting and RBSs. After my initial 11-day fast, I eventually settled into 3 days fasting/4 days OMAD, usually the RBS, each week. I expect I'll keep improving, though I'm admittedly impatient.
I'm on intermittent fasting for 2 months 18-6 every day with drinking so much more water than I normally do. Bloodtest: LDL went up from 167 to 189 and triglycerides from 58 to 106!!!
Is it because burnt fat is now in the blood or is this really worrying?
Any new ideas?
I'm in the same situation and was wondering what evolution you had.
If you can post some more info I'd appreciate
Our cholesterol guide may be helpful for you! https://www.dietdoctor.com/low-carb/cholesterol-basics
Thanks, Milan
https://www.mdmag.com/journals/internal-medicine-world-report/2011/su...
Bret Scher MD FACC Medical Director DietDoctor.com
Yes, Its a good point. Maybe it just a survive mechanism for the body, and the cholesterol work as a part of energy system.
I just had my annual blood tests done and had the same result. Been doing intermittent fasting for about a year and following keto for over 2 years - my results below show the difference in one year -
Cholesterol 262 -> 339
HDL 80 -> 71
LDL Calculated 165 -> 236
Triglycerides 84 -> 158
I just recently learned of you through my doctor. He advised me to read your book on fasting after I expressed concerns over my elevated Cholesterol. I have high cholesterol that runs in the family. Both my parents have had a heart attack/stroke in their early 60s. I am 41 and I can no longer ignore what's coming. Changing my lifestyle is a matter of life and death for me at this point. I am of average weight and height; weight a little below average, though, but I have gallbladder stones. So far, they aren't bothersome at all and my doctor told me she doesn't want to remove my gallbladder just yet because it isn't bothering me. I have read that one way to deal with gallbladder stones is to eat small meals more often. This seems counterproductive to my IF lifestyle. What if any opinion/advice do you have for people like me? Thank you,
You may find this guide helpful.
https://www.dietdoctor.com/gallstones-and-low-carb
a1c = 7.7 (after 6.6 reading last time)
Cholesterol = 214 (200 normal)
HDL = 34 (>40)
Triglycerides = 297 (<150)
LDL = 138
Chol/HDLC Ratio =6.3
Non HDL Cholesterol = 180
This was a shock as my diet has been Complete Guide to Fasting-ish before the 2-week fast. I did drop about 25 pounds, and went from a size XL to a Medium! I did not take my medications (metformin, glipizide, atorvastatin) while I was fasting.
Interested in your thoughts.
Thanks!
Fasting for longer or shorter periods immediately before the test can skew the results. If you ask for a retest, please be sure to follow their pre-test recommendations. Most recommend fasting 12-15 hours before the test.
What do you think?
Regards, Milan
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7008768/
HBP.
Your article was awakening.
Thank you for all your lectures. I am so happy there is a Doc out there who has provided fasting clinical research. I can't thank you enough. I am on a water fast. Day 20 of 40 (perhaps more depending on how I feel). I just got my blood labs back and I have elevated LDL and TC. Having worked for Pfizer, my doc wants me on Lipitor. I refuse to take this. I sold the drug. So, I am hopeful with all the fasting, I will see my cholesterol significantly reduced. I know tat diet and lifestyle choices are a huge part of this. Knowing and doing are two different things. It is time I just do it. Your lectures have greatly helped me. Really, I hope to meet you one day and shake your hand.
All the best to you and your team.
I engaged in intermittent fasting few months ago (16:8 and omad) and sustained it for 6months. When I compared my Total Cholesterol results, LDL went high from the previous results and HDL went down. I am worried because I thought that fasting would improve those digits. If you can grab a copy of some studies explaining our results, kindly furnish me with the link.
Cheers.
Jan
You may find our cholesterol guide helpful, especially the section on how to lower cholesterol naturally. https://www.dietdoctor.com/low-carb/cholesterol-basics
Please work with your doctor regarding these results. Most labs ask for only 12-15 hours of fasting before a blood draw for cholesterol. Fasting for too short or for too long a time before the blood draw may affect the results.
How long should I end an extended water fast (5 days) before I have my cholesterol blood test. I have read that fasting can temporarily increase cholesterol so my question is after ending the extended fast how long does it take for your cholesterol to return to normal?
Yes, fasting too long before bloodwork can skew your numbers. Keep in mind that we don't recommend any extended fasting without a doctor's supervision. Be sure to check with your doctor regarding fasting, as well as requirements for your blood tests.
I am confused with different information I am reading on the DietDoctor. Some contradict others. Dr Fung says that « One might (mistakenly) think that decreasing dietary cholesterol may reduce blood cholesterol levels. However, 80% of the cholesterol in our blood is generated by the liver, so reducing dietary cholesterol is quite unsuccessful. » Yet in the DD article entitled Cholesterol and
low-carb diets you mention Five ways to lower your LDL on a keto or low-carb lifestyle - Avoid Bulletproof coffee, Eat foods higher in unsaturated fats instead of saturated fats, Eat LDL-lowering keto-friendly foods, Eat more carbs…These guidelines contradict what Dr Fung is saying in this article. If you could please explain…I would appreciate it. Thank you.
Thanks for your comment! There’s a big difference between decreasing dietary cholesterol and decreasing dietary saturated fat. It seems that you may be equating the two, but they are definitely not the same.
Hi Dr. Scher. Dave Feldman's theory doesn't seem to take into account that chyolmicrons take up dietary fatty acids to distribute to cells, as well as vldl shuttling fatty acids made from de novo lipogenesis. Since dietary fat is coming in directly to cells via the chylomicrons, it doesn't seem to make as much sense that the body needs to make a lot more vldl to supply the energy needs. Maybe I am missing something.