Do you have questions about how intermittent fasting may affect your cholesterol levels? Read on to see if this dietary choice is the best decision for you and your heart health!
Intermittent fasting is extremely popular due to its ability to help with weight loss, getting blood pressure under control, lowering blood sugar level, decreasing inflammation, and more (1). But you may be wondering if intermittent fasting lowers cholesterol. Or you may be concerned if intermittent fasting can raise your cholesterol.
In this article, we will discuss what happens to your cholesterol levels when you fast.
First, let’s talk about cholesterol. Cholesterol is a waxy, fat-like substance found in your blood. You can get cholesterol from your diet, mostly from animal products, but your body also makes cholesterol.
Even though it has a bad rap, your body actually needs cholesterol for the production of certain hormones and vitamins, repairing your body, and more. In short, you need cholesterol to survive.
There are two main types of cholesterol: low-density lipoprotein (LDL) and high-density lipoprotein (HDL).
LDL is known as the “bad” cholesterol because it can accumulate in the walls of your blood vessels, causing atherosclerosis, and increasing your risk of heart attack and stroke.
HDL is known as the “good” cholesterol because it is traveling to your liver to help your body flush out cholesterol.
You’ve probably been to the doctor at some point for a blood test where they measured your total cholesterol, LDL cholesterol, and HDL cholesterol.
Understanding cholesterol levels can be tricky because of what you hear in the media and because you’ll probably see many values on your blood report related to cholesterol levels. For example, you’ll likely see total cholesterol, LDL cholesterol, HDL cholesterol, along with some ratios like HDL:triglyceride and LDL:HDL. But what do they all mean?
To start, we all are constantly hearing about how “bad” LDL cholesterol is. But did you know that you do need some LDL cholesterol for your body to properly function? Some recent studies also suggest that the compounds on LDL are more important than the amount in your body. To elaborate, some compounds on LDL can oxidize and cause an inflammatory reaction and significantly increase your risk for atherosclerosis (2).
In addition, some of these values are more important than others because they more accurately describe your risk for cardiovascular disease.
For example, even though the total cholesterol amount is important, what is more important are your individual LDL and HDL values. This is because you want your LDL levels to be low (less than 130 mg/dL) and your HDL levels to be high (above 50 mg/dL for women and above 40 mg/dL for men) (3). You could have high cholesterol but most of that coming from HDL, which would be an indicator of good health!
To make matters more confusing, there is also the HDL:triglyceride ratio and the LDL:HDL ratio. Studies have shown that these ratios are better indicators of atherosclerosis and cardiovascular disease risk than total cholesterol, LDL, and HDL levels alone (4).
This all being said, it is important to look at the whole picture when you get your results from a blood panel; a single indicator doesn’t always tell the whole story. Always talk to your doctor if you have questions about your risk of heart disease.
Let’s talk about how fasting could help with cholesterol levels.
Intermittent fasting helps you lose weight through the loss of body fat and it is pretty well known that there is a direct link between a decrease in fat mass and improvements in cholesterol values (5).
However, it appears that fasting can help with cholesterol even without weight loss. Studies show that intermittent fasting decreases the production of various compounds that are needed in order for your body to create cholesterol, especially LDL cholesterol (6, 7).
This means that there are a couple different ways that fasting could help you normalize your cholesterol levels.
Now, let’s talk about studies and what they’ve reported on fasting and cholesterol.
To be honest, conclusions on how intermittent fasting affects cholesterol levels are inconsistent. There are many studies that show how intermittent fasting can decrease your LDL levels while raising your HDL levels (8). There are also studies that show how fasting doesn’t affect cholesterol levels at all (9). Lastly, there are studies showing how fasting can increase your cholesterol levels (10).
But don’t let this scare you off from intermittent fasting!
The problem with the scientific literature with regard to intermittent fasting is that how the studies are conducted are never consistent. For example, the type of fasting, the groups of people studied, the length of the study, and the food eaten are all different. These are all factors that will affect the results.
But luckily for you, we are here to interpret these results and relay the information to you!
Ultimately, it appears that intermittent fasting will either help you lower your LDL while increasing or HDL or you will see no change in cholesterol at all.
Most of the studies that show improvements in cholesterol levels were conducted for a few weeks in overweight/obese individuals (11). And many of the studies that show no significant change were conducted in healthy individuals with normal cholesterol levels to begin with (9).
And yes, as we mentioned, there are some studies that show how intermittent fasting can cause an increase in LDL cholesterol. What’s important to note about these studies is that they were conducted for a short period of time like a few days and/or the subjects fasted completely for a short period of time (12, 13).
This means that during the first few days you start an intermittent fasting program, your cholesterol might increase but you should expect it to decrease as you stick with the diet.
This might be due to your body adjusting to your new eating pattern. As we mentioned, your body produces cholesterol and your body will change how much it makes based on a number of factors. One of those factors is stress and while you adjust to your new fasting diet, your body may be stressed, and it might start making more cholesterol(14).
Another potential reason fasting could negatively impact your cholesterol levels is because of dehydration. It appears that dehydration caused because of fasting can increase cholesterol levels. This means that you should make sure you are drinking enough fluids while fasting (15).
However, more studies are needed so that we can fully understand why this might happen.
Regardless, there are many studies that show how fasting can help you normalize your cholesterol levels so this might be a good dietary strategy for you. However, always make sure you talk to your doctor before starting any dietary change.
The bottom line is that intermittent fasting may help you lower your cholesterol levels, especially if you have higher than normal levels. If you already have normal cholesterol levels, fasting may not change your cholesterol.
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2. Rhoads JP and Major AS. How oxidized low-density lipoprotein activates inflammatory responses. Crit Rev Immunol.; 2018. [cited 2021 Jul 22] 11: 246.
3. High cholesterol: Overview. Institute for Quality and Efficiency in Health Care (IQWiG); 2017 [cited 2021 Jul 15]; Available from: https://www.ncbi.nlm.nih.gov/books/NBK279318/
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6. Motoshima H, Goldstein BJ, Igata M, Araki E. AMPK and cell proliferation - AMPK as a therapeutic target for atherosclerosis and cancer. Journal of Physiology. Wiley-Blackwell; 2006. [cited 2021 Jul 22] 63–71.
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8. Ahmed N, Farooq J, Siddiqi HS, Meo SA, Kulsoom B, Laghari AH, Jamshed H, Pasha F. Impact of Intermittent Fasting on Lipid Profile–A Quasi-Randomized Clinical Trial. Front Nutr [Internet]. Frontiers Media SA; 2020 [cited 2021 Jul 15];7:596787. Available from: /pmc/articles/PMC7882512/
9. Moro T, Tinsley G, Bianco A, Marcolin G, Pacelli QF, Battaglia G, Palma A, Gentil P, Neri M, Paoli A. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. BioMed Central Ltd.; 2016;14.
10. Jamshed H, Beyl RA, Manna DLD, Yang ES, Ravussin E, Peterson CM. Early time-restricted feeding improves 24-hour glucose levels and affects markers of the circadian clock, aging, and autophagy in humans. Nutrients. MDPI AG; 2019;11.
11. Varady KA, Bhutani S, Klempel MC, Kroeger CM, Trepanowski JF, Haus JM, Hoddy KK, Calvo Y. Alternate day fasting for weight loss in normal weight and overweight subjects: a randomized controlled trial. Nutr J [Internet]. BioMed Central; 2013 [cited 2021 Jul 15];12:146. Available from: /pmc/articles/PMC3833266/
12. L S, LE U. Fasting increases serum total cholesterol, LDL cholesterol and apolipoprotein B in healthy, nonobese humans. J Nutr [Internet]. J Nutr; 1999 [cited 2021 Jul 16];129:2005–8. Available from: https://pubmed.ncbi.nlm.nih.gov/10539776/
13. Washburn RL, Cox JE, Muhlestein JB, May HT, Carlquist JF, Le VT, Anderson JL, Horne BD. Pilot study of novel intermittent fasting effects on metabolomic and trimethylamine N-oxide changes during 24-hour water-only fasting in the FEELGOOD trial. Nutr.; 2019 [cited 2021 Jul 16] 2: 246.
14. Muldoon MF, Bachen EA, Manuck SB, Waldstein SR, Bricker PL, Bennett JA. Acute Cholesterol Responses to Mental Stress and Change in Posture. Arch Intern Med [Internet]. American Medical Association; 1992 [cited 2021 Jul 16];152:775–80. Available from: https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/616157
15. Campbell NR, Wickert W, Magner P, Shumak SL. Dehydration during fasting increases serum lipids and lipoproteins. Clin Invest Med; 1994 [cited 2021 Jul 16]; 6: 570-576.
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