OBESITY AND NUTRITION: Edited by Caroline ApovianIntelligence and obesity which way does the causal direction go?Kanazawa, Satoshi Author Information Department of Management, London School of Economics and Political Science, London, UK Correspondence to Satoshi Kanazawa, Managerial Economics and Strategy Group, Department of Management, London School of Economics and Political Science, Houghton Street, London WC2A 2AE, UK. Tel: +44 (0)20 7955 7297; e-mail: [email protected] Current Opinion in Endocrinology & Diabetes and Obesity: October 2014 - Volume 21 - Issue 5 - p 339-344 doi: 10.1097/MED.0000000000000091 Buy Metrics Abstract Purpose of review The negative association between intelligence and obesity has been well established, but the direction of causality is unclear. The present review surveys the recent studies on the topic with both cross-sectional and longitudinal data in an attempt to establish causality. Recent findings Most studies in the area employ cross-sectional data and conclude (without empirical justification) that obesity causes intellectual impairment. The few studies that employ prospectively longitudinal data, however, uniformly conclude that lower intelligence leads to BMI gains and obesity. A close examination of three such studies, from three different nations (Sweden, New Zealand, and the UK), leaves little doubt that the causality runs from low intelligence to obesity. Summary The conclusion in previous studies that obesity impairs cognitive function stems from improper interpretation of a negative association between intelligence and obesity from cross-sectional studies. Results from the analyses of high-quality, population-based, prospectively longitudinal data firmly establish that low intelligence increases the chances of obesity. Copyright © 2014 Wolters Kluwer Health, Inc. All rights reserved.