American Diet Quality Falls When Economic Conditions Improve

Does population health change with macroeconomic trends? Numerous studies have tried to answer the question whether economic conditions are associated with health outcomes, and the results might be counterintuitive for many people. Past research has shown that economic downturns are often accompanied by lower overall mortality rates and improvements in some measures of physical health. Evidence on causal pathways remains far from settled. One proposed pathway is through improved health behaviors; for example, reduced smoking, loss of excess body weight, and increased leisure-time physical activity during economic downturns.

In our recent study published in the Journal of the Academy of Nutrition and Dietetics, we investigated the relationship between macroeconomic conditions and diet quality among American adults from 1999 to 2018. The period of our study included the largest economic swings in the last 80 years, with both the Great Recession and a recovery. While previous research has focused on diet quality over time, we wanted to look at cyclical changes related to macroeconomic conditions.

We analyzed data from the National Health and Nutrition Examination Survey (NHANES). This biennial survey interviews a cross-section of American adults to recall what foods they have eaten in the last 24 hours. The data capture demographic information including sex, age, race/ethnicity, income, and education level. Diet quality was assessed with the United States Healthy Eating Index (HEI-2015), which measures the extent to which an individual’s diet complies with the 2015-2020 Healthy Eating Guidelines from the U.S. Department of Health and Agriculture. The highest HEI-2015 score one can get is 100, representing a perfect adherence to the guidelines.

What we found is that Americans had healthier diets when unemployment rates were at high levels, and diet quality at the population level deteriorated under improving macroeconomic conditions.

What we found is that Americans had healthier diets when unemployment rates were at high levels, and diet quality at the population level deteriorated under improving macroeconomic conditions. While American diets steadily improved from 1999 to 2012, the quality of the American diet started to drop in 2013 and reached a 20-year low in 2018. Overall, the highest HEI-2015 score for US adults was 51.7 in the 2011/2012 wave when unemployment rates were soaring, and the lowest was 49.35 in the 2017/2018 wave after the economy recovered.

Some might wonder, could the differences in HEI-2015 scores over time be the product of compositional changes across NHANES waves? For example, the percentage of interviewees with less than a high school education in NHANES decreased 1999 to 2018, and lower educational level has been found to be associated with poorer diet quality. To account for the demographic changes across NAHNES waves, we controlled for sex, age, race/ethnicity, and educational level in the main analysis, which makes the trend of HEI-2015 scores independent from the aforementioned variables.

A plausible explanation for the observed trends is that more people prepared food at home and dined less frequently at restaurants. Economizing and cooking at home may result in more inconvenience, but it does not imply deteriorating diet quality. Home-cooked food becomes more attractive and economical during worse economic times. More frequent cooking at home is associated with better diet quality among both lower-income and higher-income adults.

More studies are certainly needed to establish the pathways, and it will be interesting to see if the diet quality trend holds during the COVID-19 pandemic. With so many restaurants closed during the first wave of the COVID-19 pandemic, we suspect that even more significant changes in diet quality may have occurred.

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