If a factor can't explain why non-Hispanic Asians have much lower prevalence of obesity than any other race, I tend not to trust it. Are Asians simply using less plastic than other races? Look at the chart: https://www.cdc.gov/nchs/data/databriefs/db288.pdf The chart is simply striking. We should all be investigating what are the Asians doing right that all of us should learn from.
Why not genetics?
When someone tells you otherwise, it’s a good sign they don’t understand statistics. (Scientists commonly don’t understand statistics, since it’d be harder to get papers published if they did.)
Strictly speaking it’s never true, because the environment could always contain a cure for your genetic disorder and your environment just happens to not have contained one so far in your life.