Health Insurance and the Obesity Externality

Jay Bhattacharya, Neeraj Sood

NBER Working Paper No. 11529
Issued in August 2005
NBER Program(s):Health Care, Health Economics

If rational individuals pay the full costs of their decisions about food intake and exercise, economists, policy makers, and public health officials should treat the obesity epidemic as a matter of indifference. In this paper, we show that, as long as insurance premiums are not risk rated for obesity, health insurance coverage systematically shields those covered from the full costs of physical inactivity and overeating. Since the obese consume significantly more medical resources than the non-obese, but pay the same health insurance premiums, they impose a negative externality on normal weight individuals in their insurance pool.

To estimate the size of this externality, we develop a model of weight loss and health insurance under two regimes——(1) underwriting on weight is allowed, and (2) underwriting on weight is not allowed. We show that under regime (1), there is no obesity externality. Under regime (2), where there is an obesity externality, all plan participants face inefficient incentives to undertake unpleasant dieting and exercise. These reduced incentives lead to inefficient increases in body weight, and reduced social welfare.

Using data on medical expenditures and body weight from the National Health and Interview Survey and the Medical Expenditure Panel Survey, we estimate that, in a health plan with a coinsurance rate of 17.5%, the obesity externality imposes a welfare cost of about $150 per capita. Our results also indicate that the welfare loss can be reduced by technological change that lowers the pecuniary and non-pecuniary costs of losing weight, and also by increasing the coinsurance rate.

download in pdf format
   (252 K)

email paper

Machine-readable bibliographic record - MARC, RIS, BibTeX

Document Object Identifier (DOI): 10.3386/w11529

Published: Bhattacharya, Jay and Neeraj Sood. “Health Insurance and the Obesity Externality.” Advances In Health Economics And Health Services Research 17 (2007): 279-318.

Users who downloaded this paper also downloaded* these:
Bhattacharya, Bundorf, Pace, and Sood w15163 Does Health Insurance Make You Fat?
Cawley and Meyerhoefer w16467 The Medical Care Costs of Obesity: An Instrumental Variables Approach
Bhattacharya and Bundorf w11303 The Incidence of the Healthcare Costs of Obesity
Bhattacharya and Packalen w13863 The Other Ex-Ante Moral Hazard in Health
Bhattacharya, Bundorf, Pace, and Sood Does Health Insurance Make You Fat?
NBER Videos

National Bureau of Economic Research, 1050 Massachusetts Ave., Cambridge, MA 02138; 617-868-3900; email:

Contact Us