This project examines whether individuals' amount of activity energy expenditure (AEE) is related to adiposity and adiposity/diabetes-related hormones in a diverse sample of 2500, and to test the ecological hypothesis that a decline in levels of AEE is an important cause of the increases in obesity that are currently taking place in many societies.

One goal is to use doubly labeled water and/or accelerometers to objectively measure activity energy expenditure in community samples from five adult populations across the spectrum of obesity risk. From each site, (i.e., Ghana, South Africa, Seychelles, Jamaica, and the US), 500 black adults will be recruited. Among all participants, AEE will be measured using accelerometers and in a subset of 75 per site, AEE will also be measured by doubly labeled water.

The doubly labeled water sample will be used to confirm site-specific concordance with the accelerometer measurements and to estimate population mean levels of AEE. Additionally, body composition, dietary intake, fasting glucose, insulin, adiponectin, leptin and ghrelin will be measured. The relationships between calories expended in activity and body composition, dietary intake, glucose, hormones and adipocytokines, both within and between each population using doubly labeled water and accelerometers will be examined. In this longitudinal study, weight will be measured at 12 and 24-months, and AEE by accelerometer will be assessed at enrollment and again at 2-years of follow-up; associations between change in AEE and change in weight will be estimated.

The central purpose of this project is to test whether AEE or change in AEE can be identified as a contributory mechanism to population-wide weight gain and, if so, to quantify its importance. In addition, we seek to understand the interrelationships between the adipocytokines and the hormones ghrelin and insulin as well as AEE in the regulation of body weight across the continuum of body mass indices (BMI) represented by these five populations.