Posts Tagged ‘Causes of Obesity’

Chemicals may be making people obese

September 15, 2022

Roughly 40 percent of American high school students were overweight by the time they started high school.  An estimated one-third of American youth age 17-24 are ineligible for military service because of obesity.

Worldwide, the incidence of obesity has tripled since the 1970s.  Experts estimate that by 2030, one billion people worldwide will be obese.

This matters.  Obesity is related to high blood pressure, diabetes, heart disease and other serious health problems.

Part of the reason for the obesity increase is that, compared to previous generations, people nowadays are more sedentary and eat more processed foods high in sugar, fat and salt.  But this can’t be the whole reason.

In the USA, the rise in obesity affects not only people, but their cats and dogs, and rats and mice in the wild.  It affects laboratory animals that are fed controlled diets.

Mark Buchanan of Bloomberg News reported that some scientists think obesity is caused by chemicals called “obesogens,” which, even in tiny amounts, boost the production of specific cell types and fatty tissue.

An example is a chemical called tributyltin, or TBT, which is found in wood preservatives.  In experiments exposing mice to low and supposedly safe levels of TBT, a scientist named Bruce Blumberg and his colleagues at the University of California, Irvine, found significantly increased fat accumulation not only in the exposed mice, but in the next three generations.

TBT and other obesogens trigger such effects by interfering directly with the normal biochemistry of the endocrine system, which regulates the storage and use of energy, as well as human eating behavior, Buchanan wrote.

Obesogen chemicals are found in plastic packaging, clothes and furniture, cosmetics, food additives, herbicides and pesticides.  Buchanan said nearly 1,000 obesogens have been identified in studies with animals or humans.  

That would explain why laboratory animals get fat.  There might be obesogens in their food or the structure of their cages.

If this is true, it is a big, big problem.  Fixing it would require a virtual revolution in testing and manufacturing.


Plastic Might Be Making You Obese by Mark Buchanan for Bloomberg News.  Another version.

Plastic Might Be Making You Fat by Alex Tabbarok for Marginal Revolution.

The Animals Are Also Getting Fat by Alex Tabbarok for Marginal Revolution. (2013)

Why aren’t medical breakthroughs in obesity a bigger deal? by Matthew Yglesias for Grid.  [Added 09/17/2022]

Why are even the animals getting fat?

August 12, 2013

The World Health Organization predicts that, in a few years, obesity-related diseases—diabetes, heart disease, strokes and kidney failure—will be the world’s major causes of death.

The reason most commonly given for the increase in obesity, especially in the United States, is that people don’t get enough exercise or eat healthy food.

Fat CatBut a research team headed by a bio-statistician named David B. Allison has found that American animals also are getting fatter—pet dogs and cats, alley rats, laboratory mice, and marmosets, chimpanzees, macaques and vervet monkeys in primate research centers.

Now it could be the case that pet dogs and cats are not getting enough exercise, and alley rats are eating more junk food.  But what about the primates and the laboratory mice?  They live in controlled environments in which their diet and activities don’t change from year to year.

Obviously people who exercise regularly and eat fresh fruit and vegetables will on average be healthier than those who don’t.  But scientists are coming to doubt that exercise and diet alone are the keys to the obesity epidemic.   They look for biochemical factors that cause the body to store more fat.

Allison’s team studied 12 different animal populations, subdivided into male and female.

The biggest weight gainers were the chimpanzees, whose average weight increased 33.6 percent every 10 years.  Marmosets gained 9.3 percent and vervet monkeys gained 8.8 percent.  Macaques gained an average of 11.5 percent per decade in a California primate research center, 9.6 percent in an Oregon center and 5.3 percent in a Wisconsin center.

Cats gained 9.7 percent and dogs gained 2.8 percent

Laboratory mice gained 12.5 percent and laboratory rats gained 3.4 percent.  Feral city rats gained 6.9 percent and feral country rats gained 4.8 percent.

The only sub-group to show no appreciable weight gain over the decades were female laboratory rats, with an average increase of only 0.2 percent every 10 years, barely enough to measure.  Male rats gained an average of 6 percent per decade.

David Berreby, writing in Aeon magazine, reviewed some possible factors.  Stress and sleeplessness, for example, are linked to disruptions in leptin, the hormone that tells the body when it has had enough to eat.   The prevalence of artificial light, interfering with natural sleep and biological rhythms may be a factor.

Other possibilities are a virus, bacteria or industrial chemical.  Candidates include Bisphenol-A (BSA), a chemical found in most household plastics, and the Ad-36 virus, an endocrine disrupter. If there is a common factor affecting humans and animals, my guess is that these are the most likely.

But at this point we just don’t know.