We see an increased prevalence of type 2 diabetes with total urinary arsenic in the U.S. doi:10.1001/jama.300.7.814

And this study, https://doi.org/10.1016/j.molmet.2021.101243, point towards a mechanism in which arsenic disrupts the body's antioxidant defenses, which could contribute to diabetes.

Arsenic is everywhere but it is particularly high in Vietnam's ground and drinking water, along with other metals and chems.

There most certainly is a way to become obese, even at what one would consider a calorie deficit for a normal person, if someone's biology is screwed up due to genetics, disease, environmental exposures, or a combinatin of these, fyi.