[autoexec]

Lab animals kept on strict diets and routines for decades have been mysteriously gaining weight as well. (https://www.nature.com/articles/news.2010.628)

There's more than just social acceptance of obesity and pajamas in the grocery store at work.

[borroka]

Increased calorie consumption is the offender, there is little doubt about that. By carefully measuring food, one loses and gains weight accordingly (taking into account age, physical activity, etc.).

The social acceptability of being fat leads to psychologically easier consumption of calories. Personally, if it were not for the shame I would feel, I would eat 1 kg of ice cream every night. I have a great appetite, but also a great capacity for restraint.

The "mysterious weight gain" not explained by calories is, at this point, rather speculative.

[autoexec]

> By carefully measuring food, one loses and gains weight accordingly (taking into account age, physical activity, etc.)

That was the problem. The lab animals have had their food careful measured for several decades with essentially the same food/lifestyle, but weight was being gained at a rate higher than other animal populations. Because it's unknown the "why" part is speculative, but they've got some interesting ideas. Changes in animal husbandry standards, endocrine-disrupting chemicals and infectious agents were considered as possible factors.

From the study:

"There are multiple conceivable explanations for these observations. Feral rats could be increasing in weight because of selective predation on smaller animals 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." (https://royalsocietypublishing.org/doi/full/10.1098/rspb.201...)