Why immigration makes you sick:
In sum, whatever it is about American life that makes African-Americans and native-born Latinos sicker, on average, than your average white person—recent studies show higher rates of obesity, diabetes, and hypertension—eventually drags down new arrivals as well. Acculturation to American life signifies regression to the health mean of one's ethnic group.
Reaching for explanations, scientists have suggested that immigrants are a self-selected bunch—immigration officials play some role in selecting out the sickly—who must be especially hardy to make a difficult transition to a new land. Also, while they come from countries where infectious disease shortens lives, people from Third World countries have the advantage of belonging to cultures where people stay married longer; live in larger households with more family members; use fewer drugs, cigarettes, and alcohol; and eat less fat. These are all healthy behaviors. Over time here, however, these immigrants become more like Americans—hardworking single and divorced McDonalds eaters. In their home countries, immigrant women tend to smoke, drink, and divorce less than they do here; with sexual equality, apparently, come some bad habits. The discrimination and related stress that blacks and Hispanics contend with in the United States is also part of the mix of explanations for their deteriorating health.