Dahlborn, K., van Gils, B. A. A., van de Weerd, H. A. et al. 1996. Evaluation of long-term environmental enrichment in the mouse. Scandinavian Journal of Laboratory Animal Science 23(Supplement 1), 97-106. (Conference Paper)

It appears that mice who were enriched with both objects [nest box and plastic tube] and nesting material were more active, and spent less time on feeding and drinking, and they weight less compared to the other groups. .. It has been discussed earlier that laboratory animals kept during standard conditions eat more because of boredom than enriched animals.