Not saying its an obligation. But people more often than not peoole adhere closely to their culture. To a point we are all subject to our environmentand cultures. If it was very easy obesity wouldn't be on the rise in general around the world. Our bodies have hormonal responses to salt sugar and fat.

This is a really complicated topic. I would recommend if it really interets you that you do some in depth study on the history of slavery in the Untied states and the fall out after the civil war. The discrimination and the opression that followed officially well into the 1960s. There's a greater lacknof understanding of nutrition and access to healthy foods among poor people in general and black people in the United States have been disproportionately poor.

As well as how current food trends developed in the Untied States.

Its very complicated we all have free will, however most humans conform to their environment and culture.

Theres no one simple answer. There are many factors some to do with individual choice and also outside forces.