What does it mean when the experts in the documentary state that obesity is a condition because of the interaction of genes with the environment?

The documentary mentioned a higher level of obesity in the Bronx than in the Upper West Side neighborhood in Manhattan; why do you think this occurs?

The documentary stated that in the $1970$ s$,$ only $5\%$ of children were obese. Now, $30\%$ of children in the U$.$S$.$ are obese. What factors do you think have contributed to this increase in obesity in children?

You can answer the questions in one clear paragraph or answer each question separately. Each part requires a one$-$page write$-$up for two full pages $($font $12,1\mathrm{.}5$ space max.$).$Please help for this questions regarding to the dicumentary"The weight of the nation part $1$ consequences" thanks