Animals Are Mysteriously Getting Fatter

animal obesityOur 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. Female rats experienced a 7.22 per cent per decade increase in body weight, along with a 26 per cent increase in the odds of obesity.

The authors do something very clever, they gather data on the weight of control mice used in many different experiments over decades. Among mice in control groups in the National Toxicology Programme (NTP), there was a 11.8 per cent increase in body weight per decade from 1982 to 2003 in females coupled with a nearly twofold increase in the odds of obesity. In males there was a 10.5 per cent increase per decade.

Control mice are typically allowed to feed at will from a controlled diet that has not varied much over the decades, making obvious explanations less plausible. Could mice have gained weight due to better care? Possibly although that is speculative.

More generally, there are specific explanations for the weight gain in each of the animal populations, just as there are for humans. Each explanation looks plausible taken on its own but is it plausible that each population is gaining weight for independent reasons? Could there instead be a unifying explanation for the weight gain in all populations? No one knows what that explanation is: toxins? viruses? epigenetic factors?

19 Comments on "Animals Are Mysteriously Getting Fatter"

  1. Steve Stark | Aug 13, 2013 at 10:20 am |

    Morphic resonance.

  2. Anarchy Pony | Aug 13, 2013 at 10:56 am |

    Smart money is on some sort of pollutants.

    • Jin The Ninja | Aug 13, 2013 at 12:37 pm |

      you couldn’t possibly be suggesting that pesticides are AHEM! harmful!

      nor could it POSSIBLY be implied that feeding 98% grain matter to ruminants, omnivores and carnivores could cause weight gain!?!?

      i am aghast at that kind of radical logic!

      • Anarchy Pony | Aug 13, 2013 at 2:31 pm |

        I wouldn’t dream of such dissension! I think Earthstar is right on the money about the endocrine disruptors though.

  3. Cortacespedes | Aug 13, 2013 at 11:08 am |

    Bisphenol A, perhaps.

  4. Plastics.

  5. emperorreagan | Aug 13, 2013 at 11:16 am |

    High fructose corn syrup! GMOs! Gay marriage causing bestiality!

  6. Earthstar | Aug 13, 2013 at 11:31 am |

    it’s most likely due to endocrine disrupting chemicals from plastics and industry. Estrogen mimicking chemicals cause weight gain. they’re in all the waters and throughout the food chain now.

    • sambrown299 | Aug 13, 2013 at 4:45 pm |

      Also all the soy in foods, soy is an estrogen producer.

    • Trismegistus | Aug 14, 2013 at 1:32 am |

      Hey. But what about fish? who are exposed and consume far more plastic than any mammal… They are becoming smaller. Your hypothesis is false. Not to mention the absorption factor of ocean plastics, ddt, prozac, and plenty of “estrogen” (quotations because estrogen is not necessarily the cause of fat gain) metabolizing chemicals.

  7. BuzzCoastin | Aug 13, 2013 at 11:54 am |

    > there was a 11.8 per cent increase in body weight per decade from 1982 to 2003

    the same period GMO crops entered the food supply & increased exponentially
    HFCS started to be used in place of sugar at that time too
    aMerkins now consume the same amounts of food
    but the food now has a higher calorie content thanks to GMO grains

    • emperorreagan | Aug 13, 2013 at 12:43 pm |

      According to the department of agriculture, we eat more of everything except eggs over the period.

      There’s some trade-off (less milk, more cheese), but overall numbers are higher.

      Compared to the 50s, there’s huge jumps in grains, meat, fruit & vegetable, and fat consumption.

      • BuzzCoastin | Aug 13, 2013 at 12:53 pm |

        true, we are eating more of some foods & less of others
        e.g: HFCS consumption has increased significantly
        but there is a practical limit
        to the poundage of food humans can eat
        normally around 1000-1500 lbs a year
        and Pollan in “Omnivores Dilemma” points out
        the poundage now has a higher calorie content than before GMOz

        • emperorreagan | Aug 13, 2013 at 1:38 pm |

          When you add up the figures in the USDA sheet for average per capita consumption, they are pushing 1500 lbs. So consumption at the high range + more calorie dense GMO and processed foods + I would guess a decline in calories burned per day because of the changing nature of American labor makes the change in human weight obvious. It only makes sense that animals that are partly/wholly reliant on human waste and scrap would also be heavier.

          The change in lab rat weight is interesting because it would indicate some other mechanisms at work. The food is controlled for macro-nutrients and calories, so that could very well be a product of something like how a GMO grain is processed or one sugar versus another.

          • BuzzCoastin | Aug 13, 2013 at 2:58 pm |

            the lab rat change has to have a link to GMO grain
            what else changed if the diet is basically the same?

            most people consume way more food than necessary
            mainly because it’s readily available, convenient & cheap
            and work less physically
            because machines are available, convenient & relatively cheap
            this all adds up to fat, dumb & happy
            too bad the people at the top are the same

  8. Growth hormones from the dairy and livestock industry landing in our water supply.

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