Archived Lecture: The Omnivore’s Predicament: Body Weight Regulation and Cognitive Control
Timothy A. Johnson Medical Scholar Lecture presented by the Fralin Biomedical Research Institute at VTC and the Virginia Tech Carilion School of Medicine
About this Seminar
Homeostatic models of weight regulation fail to account for the substantial worldwide increase in obesity caused by the abundance of inexpensive calories over the past 50 years. Even staples such as milk demonstrate price elasticity, meaning that consumption is price-sensitive. Evidence from psychology, cognitive neuroscience, and neuroeconomics points to a role of cognitive factors in the control of body weight in humans. The defense of negative energy balance appears to be mostly homeostatic: peptide hormones such as ghrelin, leptin and insulin rapidly signal weight loss to the CNS to promote increased appetite. However, what explains the defence against weight gain, and why has it failed recently?
Dr. Dagher will argue that food overconsumption in both hunter-gatherers and agricultural societies is economically sub-optimal. Indeed, foraging models have long shown that animals in the wild do not overconsume, but rather accumulate energy stores to an optimum point, e.g. when the risk of starvation equals the risk or death from predation. In humans, the cost of food (in money, time or effort) always made overconsumption suboptimal. However, modern economic factors have allowed calorie overconsumption: (1) food processing technology and marketing allowing sellers to manipulate energy content and taste, (2) availability of cheap calories thanks to agricultural subsidies and technological advances, and (3) economic growth driving increased consumption.
Dr. Dagher will provide evidence that prefrontal systems involved in value computation and motivation act to limit food overconsumption when food is scarce or expensive, but promote over-eating when food is abundant. He will review the genetic and neuroscience literature on the CNS control of body weight. He will also present three recent studies: (1) prefrontal and temporal lobe cortical thickness correlate with BMI and comprise a largely heritable phenotype; (2) successful weight loss correlates with activation of the DLPFC, deactivation of VMPFC, and their functional connectivity; (3) a homeostatic peptide, ghrelin, promotes food-odour conditioning by increasing reward prediction error signals. Finally, he will review evidence that adiposity affects brain structure and function which may explain its role as a risk factor in dementia.
This is a free event hosted by the Fralin Biomedical Research Institute and the Virginia Tech Carilion School of Medicine. The Timothy A. Johnson Medical Scholar Lecture Series hosts clinician scientists who are exploring frontiers of medicine. These lectures are principally intended for Virginia Tech Carilion School of Medicine students and Virginia Tech students in Translational Biology, Medicine, and Health graduate program. Virginia Tech and Carilion Clinic faculty, staff, and students may also attend.
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Alain Dagher, M.D.
Professor, Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University