Weight gain is usually blamed on poor diet and a lack of exercise. But the marmosets and macaques living at a Madison, Wis., laboratory have followed the same diet and exercise regimens since 1982. Still, they grew heavier with each passing decade, leading David B. Allison, a biostatistician at the University of Alabama at Birmingham, to believe that environmental factors may be at play. He and his colleagues studied weight changes in 20,000 animals, including primates and rodents used for research, domestic cats and dogs, and urban feral rats. They tracked the animals’ percentage weight gain per decade, as well as their odds of being obese. Both showed a strong upward tendency. Chimpanzees grew 33.6 percent heavier per decade; mice grew 12.46 percent heavier.

Allison speculates that factors such as endocrine-disrupting toxins in the water supply or pathogens affecting mammalian metabolism may be to blame. But some say his data could be explained by diet and ex­ercise changes—caused, perhaps, by an increase in the numbers of lab animals being housed in a single cage. Allison agrees that housing might affect metabolism, but humans, too, live in increasingly crowded conditions. “This is exactly the kind of innovative thinking ... we think our results warrant,” he says. “If density of housing affects weights in animals, maybe density of housing also affects body weight in humans.”

This article was originally published with the title Does This Collar Make Me Look Fat?.

5 Comments

1. 1. bfahrn 06:02 PM 2/4/11

   I have 4 cats of different ages. They all eat out of the same bowls of dry cat food. They go outside in the yard and woods whenever they want, sometimes catch rodents, small lizzards and insects and chew bits of grass. I think this outside is the reason for their trim figures and health, compared to cats kept always indoors I observe at places I visit, some of whom have sagging bellies and listless disposition.
   It is just not right to keep animals of this sort indoors. It's done so I say nothing. But I've yet to see a Fat-Cat who can get outside and run around.
   Just like some people I know!

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2. 2. Cosmoknot 10:02 PM 2/4/11

   If density of housing were to affect body weight in humans, then overpopulated countries like Bangladesh would be overpopulated with overweight people, but that is not the case.
   It sounds like another modernization curse. Like cell phone brain tumors. Something caused by all the electromagnetic garbage surrounding us all the time. The ever increasing satellite signals and wifi put stress on our bodies, so it's either don a tinfoil hat or put on excessive pounds to block the radiation.

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3. 3. Quinn the Eskimo 02:15 AM 2/5/11

   Prop me up in the corner of the sofa! Even I look fat sitting like that!
   
   Oh, wait. . .Never mind.

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4. 4. mrbarletta 01:02 PM 2/6/11

   @cosmoknot The writer says is a exercise and diet change due to the housing conditions. I don't know if a housing condition will trigger the same change in bangladesh, nor if they can choose not to eat rice or increment their 2000 calories ..
   i think its feasible, housing condition triggers diet-exercise habit.. my 2c

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5. 5. Graetz 10:44 AM 2/8/11

   Could the use of hormones and maybe other additives being added to feed for commercial animal feed to get faster growth be effecting lab animals and even people as well?

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