Here's a study showing that exercise reduces gallstone development in mice.

I've read many times that a sedentary lifestyle is ASSOCIATED with higher risk for gallstones, but here's is more concrete evidence that shows an actual effect of exercise itself, not merely an association.

Keep in mind the mice in the study ran for 45 min/day *every* day for 12 weeks, but less exercise than that should still prove useful.

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Endurance exercise training reduces gallstone development in mice.
Wilund KR, Feeney LA, Tomayko EJ, Chung HR, Kim K.

Department of Kinesiology and Community Health, University of Illinois, 906 S. Goodwin Ave., Urbana, IL 61801, USA. kwilund@uiuc.edu

Gallstones form when the ratio of bile cholesterol to bile acids and phospholipids is elevated, causing cholesterol to precipitate. Physical inactivity is hypothesized to increase gallstone development, but experimental evidence supporting this is lacking, and potential mechanisms for the antilithogenic effects of exercise have not been described. The purpose of this study was to examine the effect of endurance exercise training on gallstone formation and the expression of genes involved in bile cholesterol metabolism in gallstone-sensitive (C57L/J) mice. At 10 wk, 50 male mice began a lithogenic diet and were randomly assigned to an exercise-training (EX) or sedentary (SED) group (n = 25 per group). Mice in the EX group ran on a treadmill at approximately 15 m/min for 45 min/day for 12 wk. At the time animals were euthanized, Gallstones were collected, pooled by group, and weighed. The weight of the Gallstones was 2.5-fold greater in the SED mice compared with EX mice (143 vs. 57 mg, respectively). In the EX mice, hepatic expression of the low-density lipoprotein receptor (LDLr), scavenger receptor class B type 1 (SRB1), and sterol 27 hydroxylase (Cyp27) was increased by approximately 2-fold (P < 0.05 for each). The LDLr and SRB1 increase cholesterol clearance by low-density lipoprotein and high-density lipoprotein particles, respectively, while Cyp27 promotes the catabolism of cholesterol to bile acids. Taken together, these data indicate that exercise promotes changes in hepatic gene expression that increase cholesterol uptake by the liver but simultaneously increase the catabolism of cholesterol to bile acids, effectively reducing cholesterol saturation in the bile. This suggests a mechanism by which exercise improves cholesterol clearance from the circulation while simultaneously inhibiting gallstone formation.

http://www.ncbi.nlm.nih.gov/pubmed/18187606