John's primary field of research is health economics, with a focus on the economics of obesity. He studies the economic causes of obesity, the economic consequences of obesity, and economic approaches to obesity treatment and prevention. Examples of research projects include: the effects of food advertising on diet and of income on weight; the impact of obesity on labor market outcomes such as wages; the effect of physical education on youths; and the effectiveness of financial rewards for weight loss.
John's research has been published in general-interest economics journals (American Economic Review, Review of Economics and Statistics, Journal of Economic Perspectives) as well as journals in health economics (Journal of Health Economics, Health Economics), labor economics (Journal of Human Resources, Labour Economics), public policy (Journal of Policy Analysis and Management) and health policy (Health Affairs, Journal of Health Politics, Policy, and Law). He serves as co-editor of the journal Economics and Human Biology.
His research has been supported by grants from the following sources: the National Institutes of Health; the Robert Wood Johnson Foundation; the Economic Research Initiative on the Uninsured; the IBM Center for the Business of Government; the Merck Foundation Center on Consumers, Pharmaceutical Policy, and Health; the University of Michigan Retirement Research Consortium; the U. S. Department of Agriculture; the Institute for the Social Sciences and the Bronfenbrenner Life Course Center at Cornell University; and J. P. Morgan Private Bank Global Philanthropic Services.
John's research has been featured in stories in the Wall Street Journal, Financial Times, New York Times, Business Week, Forbes, Scientific American, Chronicle of Higher Education, as well as on radio and television.