Julia Belluz writes in The obesity trend isn’t only affecting humans — chimps, pets, and lab rats are getting fatter too for Vox:

We spend a lot of time talking about how fat one type of animal has gotten in recent years: humans. But what about all the other animals living near people — have they gained weight, too?


Maybe domestic pets and feral rats fattened up because the availability of food has increased over the years. But how does that explain why lab animals in controlled environments got heavier, too?

Is the claim that lab animals, who lived in a controlled environment without a change in their diets, gained weight a consensus view?

  • We can imagine confounding factors. Maybe the common temperatures of the labs have changed over the years, along with heating technology for buildings. If the lab animals are fed with a certain food (say barley), maybe the nutritional value of barley has improved over the years, along with agriculture in general.
    – GEdgar
    Jan 15, 2022 at 11:16

1 Answer 1


The publication The Atlantic also claims that laboratory animals are getting heavier, as well as pets and other animals.

Animals in strictly controlled research laboratories that have enforced the same diet and lifestyle for decades are also ballooning.

and it refers to a research article published in 2010 by The Royal Society:

Canaries in the coal mine: a cross-species analysis of the plurality of obesity epidemics

A dramatic rise in obesity has occurred among humans within the last several decades. Little is known about whether similar increases in obesity have occurred in animals inhabiting human-influenced environments. We examined samples collectively consisting of over 20 000 animals from 24 populations (12 divided separately into males and females) of animals representing eight species living with or around humans in industrialized societies. In all populations, the estimated coefficient for the trend of body weight over time was positive (i.e. increasing).
. . .
Similarly, we examined whether body weight increases were greater for laboratory versus non-laboratory animals. The non-laboratory animals included urban rats, rural rats, and domestic cats and dogs. Again, we compared the meta-analytically derived estimates for each of these groups, and find that the laboratory animals show a greater increase in per cent weight gain and odds of obesity than non-laboratory animals.
. . .
There are multiple conceivable explanations for these observations. Feral rats could be increasing in weight because of selective predation on smaller animals [22,23] or because just as human real wealth and food consumption have increased in the United States, rats which presumably largely feed on our refuse, may also be essentially richer. But these factors cannot account for the findings in the laboratory animals that are on highly controlled diets, which have varied minimally over the last several decades.
. . .
[My bolding]

So the study found not only that laboratory animals in a controlled environment are getting obese, but more so than animals in other groups.

The OP also asks

Is the claim ... a consensus view?

The Royal Society states in a page titled Authors

The Royal Society publishes high quality, peer-reviewed journals covering all scientific disciplines. This is part of our mission in relation to the dissemination, discovery and preservation of scientific findings and ideas.

  • 1
    Proceedings of the Royal Society B is indeed peer-reviewed
    – Henry
    Jan 14, 2022 at 10:31
  • 4
    Great answer. This is a very minor nitpick, but I'm not really sure that "peer-reviewed" should be synonymous with "consensus view". Consensus is usually taken by sampling multiple experts and studies. A paper could be considered "worth publishing" by the referees but represent a non-consensus extreme. For instance, the RSC itself published (and retracted) a paper on kidney stones that did not represent the opinion of any skilled worker in the field.
    – 0xDBFB7
    Jan 17, 2022 at 13:57

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