The butyrylcholinesterase knockout mouse is obese on a high-fat diet.

Butyrylcholinesterase (BChE) inactivates the appetite stimulating hormone octanoyl-ghrelin. The hypothesis was tested that BChE-/- mice would have abnormally high body weight and high levels of octanoyl-ghrelin. It was found that BChE-/- mice fed a standard 5% fat diet had normal body weight. However, BChE-/- mice fed a diet containing 11% fat became obese. Their obesity was not explained by increased levels of octanoyl-ghrelin, or by increased caloric intake, or by decreased exercise. Instead, a role for BChE in fat utilization was suggested.