This article is from the WSSF 2015 AFRMA Rat & Mouse Tales news-magazine.

Obesity levels are on the rise not only in humans but in the animals close to them including research animals. According to researchers at the University of Alabama, Birmingham, they found during the last 50 years mice saw a 12% increase every 10 years and rats had a 3% increase, where Baltimore’s feral rats increased by almost 7% each decade. Increased body weight was found even in animals whose diet and physical activity was known to be the same during the study period. Since it is known exactly what research animals are fed and housing hasn’t changed much in 50 years, they looked for other factors causing this increase other than eating more and exercising less. Several studies have linked endocrine disruptors such as bisphenol A (BPA) and some tin-containing compounds along with a common-cold causing adenovirus to increased body mass.

Published in Proceedings B (Proceedings of the Royal Society B: Biological Sciences), 2011 Jun 7;278(1712):1626-32, Canaries in the coal mine: a cross-species analysis of the plurality of obesity epidemics.

Article Animals are getting fatter, too on The Scientist, by Carrie Arnold, Nov 24, 2010.