This is the article that the study authors linked to in their other writing: https://royalsocietypublishing.org/doi/abs/10.1098/rspb.2010...

It's certainly interesting although worth noting that all the animals examined have some close link to human-supplied food. They're all domestic pets, research animals, or rats (although I suppose the rural rats might be less so? They still show weight gain). I admit it would be hard to find something else that would be appropriate, especially given competing factors at play (e.g., the possibility of animals having shorter lifespans over time or evolving to be smaller in response to capture). Still, you'd think if it was something environmental it would show up in animals less dependent on humans for food. Interesting study.

There's a tiny bit more context here: https://www.vox.com/2015/8/24/9194579/obesity-animals

As for that article, the author makes a good point it's curious this hasn't been followed-up on.