α-Muricholic acid is a murine-specific primary bile acid. Dietary administration of soybean protein decreases fecal levels of α-muricholic acid in mice with high-fat diet-induced obesity which correlates with increases in fecal Clostridium cluster XIVa, a major producer of secondary bile acids. Plasma, liver, and muscle levels of α-muricholic acid are increased in mice switched from a high-fat to low-fat diet.