Tradeoffs in childhood energy allocation and the impact of market integration on ontogeny and health

Cuny Hunter College, New York NY

Investigators

Abstract

The Directorate of Social, Behavioral and Economic Sciences offers postdoctoral research fellowships to provide opportunities for recent doctoral graduates to obtain additional training, to gain research experience under the sponsorship of established scientists, and to broaden their scientific horizons beyond their undergraduate and graduate training. Postdoctoral fellowships are further designed to assist new scientists to direct their research efforts across traditional disciplinary lines and to avail themselves of unique research resources, sites, and facilities, including at foreign locations. This postdoctoral fellowship award supports the interdisciplinary training and research of a young scholar at the intersection of the fields of anthropology, evolutionary biology, and public health to explore the tradeoffs in childhood energy allocation and the impact of market economy on health. The way in which children manage energetic resources and respond to changing environmental conditions remains unclear. All of life's essential tasks -- maintenance, growth, reproduction, immune function, and physical activity -- require energy (i.e., calories), and it is often assumed that organisms allocate resources to these competing demands in a manner that maximizes fitness. This framework of energy allocation and tradeoffs has been widely applied to understand human biological variation. However, few studies have tested its validity among children. Addressing this limitation, the present project integrates methods and perspectives from multiple disciplines to investigate the nature of childhood energy use through the lens of allocation tradeoffs. It also applies this new synthesis to explore an important real world problem: the impact of market integration on child ontogeny and health. Utilizing a novel study design among the Shuar of Amazonian Ecuador, we pursue two primary research questions. (1) Do energetic tradeoffs exist between childhood growth, physical activity, and immune function as predicted by the energy allocation model? (2) Is market integration associated with changes in childhood energy allocation that promote overweight/obesity and poor cardiovascular health? Results will have significant implications for several scientific areas. They will also be used to develop effective health policy and relief aid in Ecuador and the United States. Promoting opportunity for training, this work involves numerous indigenous educational health forums and significant research experience for minority American undergraduates. Importantly, the project also provides scientific and professional training and for the Fellow, preparing him for a career as an independent researcher at the forefront of integrative biological science. Despite the success of previous studies investigating human biological variation using evolutionary life history theory, important gaps in our understanding of human phenotypic plasticity and energy use remain. Few studies have investigated energetic tradeoffs among children or have explored the potentially important role of physical activity in child energy dynamics. No previous life history research has incorporated accurate measurements of total energy expenditure (TEE) and resting energy expenditure (REE) into study designs, preventing assessment of several critical assumptions of the life history tradeoff model. Directly addressing these limitations, the present project aims to test the validity of the energetic tradeoff model and apply this framework to investigate the role of tradeoffs in relationships between Shuar market integration, ontogeny, and child health. We employ a novel two-week longitudinal study design among 100 Shuar children (age 5-10 years) living in two communities differing greatly in level of market integration, lifestyle, and diet. Gold standard metabolic measures of child TEE (doubly labeled water), REE (indirect calorimetry), and physical activity energy expenditure (doubly labeled water and accelerometry), as well as robust measures of weekly linear growth (knemometry), immune activity (finger-prick blood C-reactive protein, total Immunoglobulin E, and total Immunoglobulin G), cardiovascular health (finger-prick blood glucose and lipids), and energy intake and market integration (observation and interviews) will be made from each participant, supporting between-community, between-individual, and within-individual analyses of energy use and tradeoffs. This work has the ability to address many underexplored areas of research, including the relative importance of energy intake versus energy expenditure in the etiology of overweight/obesity and cardiovascular disease, the precise energetic costs of human immune activation, and, importantly, the overall validity of the life history tradeoff model.