U.S.A : Tuesday, 23 November 2010 (Local Time)
It’s not just us humans. Creatures great and small appear to be getting fatter too, according to a new U.S. study.
From domestic dogs and cats to lab mice and alley rats, many animal species are also growing in girth. And this statistically significant weight gain among diverse animal populations may be pointing to hidden environment or viral explanations for epidemic human obesity, the study’s authors say.
“It may be something in the air, the water or the food, other than the nutrients,” says David Allison, a biostatistician at the Unversitiy of Alabama at Birmingham and senior study author.
The study appeared Wednesday in the journal “Proceeding of the Royal Society B.”
The paper looked at domestic dogs and cats, feral rats, lab rodents and four species of laboratory primates including chimps.
Accessing a surprising wealth of historical weight data on the creatures, the study showed significant weight gain in all of them over the course of decades.
For example, data from a large veterinary hospital in the Northeastern U.S. showed that dogs gained nearly 3 % in body weight between 1990 and 2002. Data from the same clinic showed cats had grown almost 10 % large over a decade.
While all the animals studied are in close contact with humans, their potential access to our ubiquitous junk food cannot explain the weight gain for many of them, Allison says.
Baltimore alley rats – which have pest control weight records dating back to 1948 – are 40 % heavier now than they were in the mid-20th century. That weight gain could surely be due to the dumpsters-laden with the larded leavings of our food culture – they can currently access. But their caged, white cousins are also gaining weight, despite strict pellet diets that are virtually universal and have varied little over decades.
“Domestic dogs and cats, for example, you might say, well they live with us and we throw away more food than we ever did…and we probably pass it off to them,” Allison says. “However, that doesn’t explain why laboratory mice and rats in the National Toxicology Program…of the United Sates are getting biggger.”
Likewise, it doesn’t explain why the weight records for marmosets in the Wisconsin National Primate Research Centre showed those tiny monkey getting fatter, Allison says. “In these laboratory animals…the composition of the food is generally held constant.”
Even after adjusting for minor dietary changes in lab animal diets, the weight gains were still significant.
Allison speculates pathongens like viruses and environmental contaminants may be among the fattenning forces at work.
Indeed, Allison says, viruses like one known as adenovirus 36 have been shown to cause weigh gain in some animals. And new man-made contaminants like dioxins that disrupt the hormonal system could also be partially to blame. The use of air conditioning and heating in houses and laboratories may also be playing a fattening role, ensuring that we exert less energy than in the past to stay cool or keep warm.
Story from : www.healthzone.ca (reported by Joseph Hall)
