Our pets are becoming obese, as well as pests and vermin…but bafflingly, so have laboratory rats given the same controlled diets that have been in use for decades. Could toxins, viruses, or some other factor be at play in humans and animals living in proximity to our society growing fatter decade after decade? Marginal Revolution writes:
In a remarkable paper Allison et al. (2011) gather data on the weight at mid-life from 12 animal populations covering 8 different species all living in human environments. Dividing the sample into male and female they find that in all 24 cases animal weight has increased over the past several decades.
Cats and dogs, for example, both increased in weight. Female cats increased in body weight at a rate of 13.6% per decade and males at 5.7% per decade.
The authors also looked at animals not directly under human control such as rats. For the 1948–2006 time period, male rats trapped in urban Baltimore experienced a 5.7 per cent increase in body weight per decade and a nearly 20 per cent increase in the odds of obesity.