Yes that's probably a factor. Exposure to endocrine disruptor chemicals such as phthalates (plastic softeners) is correlated with lower testosterone levels.

https://pubmed.ncbi.nlm.nih.gov/25121464/

And we have extensive research linking low testosterone to obesity. In fact the causality appears to run both ways with low testosterone causing an increase in adipose tissue, which in turn drives a further reduction in testosterone production. Vicious cycle.

But diets have changed over time. Americans on average do consume more calories than 50 years ago, and get a higher proportion of their calories from sugars.