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I have read some webpages mentioning that intermittent fasting increases the odds of getting gallstones. E.g., https://www.hopkinsmedicine.org/health/conditions-and-diseases/gallstones:

As the body metabolizes fat during rapid weight loss, it causes the liver to secrete extra cholesterol into bile, which can cause gallstones. Fasting. Fasting decreases gallbladder movement, which causes the bile to become overconcentrated with cholesterol.

However, some other webpages mentions intermittent fasting reduces the odds of getting gallstones, e.g. https://www.drberg.com/blog/will-intermittent-fasting-cause-gallstones#Title4:

Together, keto and intermittent fasting will help keep your gallbladder healthy and go a long way toward prevention of gallstones.

Have scientific studies confirm that intermittent fasting (e.g. 16 hours of fasting per day) actually increases or decreases the odds of getting gallstones, assuming a healthy diet?

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According to the following study in 9 women, theoretically, 16/8 hour intermittent fasting could increase the risk of gallstones (the risk increases with increased cholesterol content of bile): Effects of fasting on the composition of gallbladder bile (Gut, 1980):

Mean cholesterol saturation index was significantly greater after a 15 hour fast (1.35+0.08) than after a 10 hour fast (1.05+0.10). However, after 20 hours of fasting, mean cholesterol saturation index had fallen to 1.13+0-10.

In conclusion, our findings suggest that fasting for between 10 and 20 hours may indeed increase the risk of gallstone formation, but this effect is counteracted by a more prolonged fast.

In another study mentioned in the above article, the cholesterol concentration after intermittent fasting increased only in women but not in men. To know, if intermittent fasting is actually associated with an increased risk of gallstones, clinical trials in which the increased incidence of stones would be observed, would be needed...

In another study in 9 healthy adults, after fasting for 4-6 days, the cholesterol content of bile has decreased by about 30%, but then again, from this study alone, it's not possible to conclude that such fasting regime can reduce the risk of gallstones.

"Prolonged fasting" is still considered a risk factor for gallstones, according to several sources: The Lancet, 2006, UpToDate, 2018, International Surgery Journal, 2017, Boston Children's Hospital, etc.

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  • Thanks very much! I think in the first quote they meant (1.05+0.10) instead of (105+0.10) – Franck Dernoncourt Jan 3 '20 at 16:36
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    Yes, it's 1.05 - it was a copy-paste issue from pdf. – Jan Jan 3 '20 at 16:37

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