Chunky Monkey: Lab Animals Are Getting Fatter and Scientists Don’t Know Why

Over the past few decades, lab animals have been tipping the scales.
This nap is brought to you by too many bananas.
(Photo: Kiyoshi Ota/Reuters)
Aug 27, 2013· 1 MIN READ
Shaya Tayefe Mohajer is TakePart's News Editor.

Lots of things could explain why there are so many overweight Americans—fast-food consumption, not enough exercise, our national zealotry for bacon.

Mmm, bacon.

But I digress.

None of those unhealthy habits can be blamed as the answer to one question: Why are our lab animals getting fat?

Unless lab rats are escaping captivity to feast on Twinkies (which, I admit, I kind of hope they are), it doesn’t make sense that caged animals are getting fatter.

But unlike street animals that may be feasting on trash, lab animals are gaining weight, according to Aeon Magazine.

The scales are showing higher average weight over the past decade for laboratory macaques, chimpanzees, vervet monkeys, mice, dogs, cats and rats.

For some reason, chimps are doing worst of all: Their average body weight has risen 35 percent per decade. It’s unclear whether animals used to get more exercise or conditions have affected their mood in a way that causes obesity.

Researchers believe hidden global factors might be contributing to a mysterious, widely shared cause that is making humans and other animals fatter.

That mystery cause could be just about anything as obesity researchers analyze sleeplessness, stress, intake of bisphenol-A (BPA) and other prevalent chemicals, viruses, gut bacteria or even eating at night, when our ancient ancestors were sleeping…the list goes on and on.

Scientists are also beginning to consider “roads less traveled” in obesity research, such as the creation of “thermoneutral zones,” also known as air-conditioned and heated places.

When people are in the outdoors and exposed to the elements, heat makes them sweat, cold makes them shiver and the body has to expend energy to maintain a normal internal temperature.

“Temperatures above and below the neutral zone (found in climate-controlled environments) have been shown to cause both humans and animals to burn fat, and hotter conditions also have an indirect effect: they make people eat less,” Aeon reported.

Then there’s the theory of “infectobesity,” which believes obesity may be infectious, like the flu. A virus known for causing eye and respiratory infections in people could also be infecting them with obesity. The virus, called Ad-36, has caused weight gain in chickens, rats, mice and monkeys. It hasn’t been tested on humans, but testing found that obese people are much more likely to have the antibody to the virus in their bodies.

Whatever the case may be, scientists believe attributing obesity to personal responsibility is simplistic.