Posts Tagged ‘laboratory mice’

Is Obesity Jumping Species?

June 11th, 2012

The Sunday Review of the New York Times had a fascinating piece “Our Animal Natures” by Barbara Natterson-Horowitz and Kathryn Bowers. They have an upcoming book, “What Animals Can Teach Us About Health and the Science of Healing.” They discuss how animals have many of the same diseases as humans, including cancer, addiction and cutting or self-harm. They do discuss the increase in body weight among animals. They note that animals in the wild often have cycles of gaining and losing weight. But when there is an abundance of food and access to it, weight gain will follow. This applies not only to household pets but to wild animals as well. They state, “Remarkably, it is the landscape around an animal that determines whether its weight stays steady or rises.” They speculate that it may be a interruption in circadian rhythms caused by light pollution which has brightened our planet. Or, gut microbes. NYT: Our Animal Natures

One thing their excerpt did not address was whether the increase in human obesity was also seen in animal obesity.  YC Klimentidis et al did address this in an article published in the Proceedings,Biological Science of the Royal Society last June. They examined samples consisting of over 20,000 animals from 24 populations (12 divided separately into males and females) representing 8 species living with or around human populations in industrialized societies. In all populations, the trend of body weight over time was increasing.      They calculate the probability of all trends being in the same direction by chance is 1.2 x 10-7 . They found the average mid-life body weights have risen among primates and rodents living in research colonies as among feral rodents and domestic dogs and cats. The authors conclude, “The consistency of these findings among animals living in varying environments, suggests the intriguing possibility that the aetiology of increasing body weight may involve several as-of-yet unidentified and/or poorly understood factors (e.g. viral pathogens, epigenetic factors). PubMed: Canaries in the coal mine: a cross-species analysis of the plurality of obesity epidemics

This phenomenon has implications beyond the obesity epidemic. Researchers at the National Institutes of Health have observed that many standard control rats and mice used in biomedical research are sedentary, obese, glucose intolerant and on a trajectory to premature death. This, they state, may confound data interpretation and outcomes of human studies. Fundamental aspects of cellular physiology, vulnerability to oxidative stress, inflammation and associated diseases are affected by changes in dietary intake and expenditure. PubMed: “Control” laboratory rodents ‘metabolically dead’