Does Health Insurance Make You Fat?   Policy recommendations for
interventions intended to influence body weight decisions often
assume the obesity creates negative externalities for the non-
obese. The authors build on earlier work demonstrating that this
argument depends on two important assumptions:    1. That the
obese do not pay for their higher medical expenditures through
differential payments for health care and health insurance; and
2. That body weight decisions are responsive to the incidence of
medical care costs associated with obesity.  In this paper, they
test the latter proposition—that body weight is influenced by
insurance coverage—using two approaches.  First, the study used
data from the Rand Health Insurance Experiment, in which people
were randomly assigned to varying levels of health insurance, to
examine the effect of generosity of insurance coverage on body
weight along the intensive coverage margin. Second, it used
instrumental variables methods to estimate the effect of type of
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