In this study, objective measurement tools will be used to examine the "ecology of AEE". This study will take place in 5 countries spanning the range of the activity-obesity spectrum and will combine both within-population person-level and between-population ecological analyses. First, the study will examine whether an individual's amount or pattern of AEE is related to adiposity in a diverse sample of 2,500. Second, the study will evaluate whether a decline in levels of AEE is an important cause of the rapid increases in obesity that currently take place in many societies. As an exploratory aim we will examine the role of selected adipocytokines and the appetite hormone ghrelin.