approach that does not explicitly address this simultaneous process will bias the estimated
relationship between behaviors, such as food intake or physical activity and the explanatory
variables. For that reason, we estimate these two equations simultaneously using a treatment
effects estimator. In the first equation, we run a probit regression to estimate whether an
individual chooses to manage health via medication. In the second equation, we estimate the
magnitude of diet and activity choices recommended to control diabetes. To obtain robust
variance estimates, we use STATA 9.0 to control for survey sample weights and inter strata
variation.
Data and Results
Data
Since 1999, the NHANES data have been collected annually through the Centers for Disease
Control and Prevention via the National Center for Health Statistics. Each year 5,000 civilian,
noninstitutionalized persons in the U.S receive a thorough medical examination, provide a 24-
hour dietary recall, and answer questions related to health behaviors, such as dieting, physical
activity, alcohol consumption and cigarette smoking. This survey is designed to be nationally
representative and over-samples African Americans, Mexican Americans and individuals with
low-income (United States Department of Health and Human Services, Centers for Disease
Control and Prevention, National Center for Health Statistics, 2005). Using the Pyramid servings
database, this survey can also be used to calculate the number of servings for each pyramid food
group consumed over the 24-hour period (United States Department of Agriculture, 2006). For
this study, we limit our analysis to adults, aged twenty and older1. We exclude pregnant and
1 Our analysis focuses on adults because most children do not have complete control over their food intake or level
of physical activity.
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