Examining Behavioral Phenotypes of Overeating and Obesity: Environmental, Psychological, and Neurobiological Influences on Food Motivation and Palatable Food Consumption

Abstract

Obesity is a substantial problem in the U.S., with growing rates particularly at early developmental stages (e.g., childhood, adolescents). Several factors may contribute to the development of overeating and obesity, including elevated craving in response to food-related cues, individual susceptibility to food-related cues, and neural changes associated with behavioral phenotypes implicated in obesity. The current dissertation aims to shed light on these contributing factors, in an effort to better understand obesity risk and contribute to the development of effective interventions. Study 1 aimed to test the incentive-sensitization theory of addiction by examining food motivation, hunger, and consumption in a cue-rich compared to neutral environment. Participants (n = 126) were randomized to either a naturalistic fast-food laboratory or a neutral laboratory, where they provided self-reported ratings of “wanting,” “liking,” and hunger, and engaged in a task assessing food motivation and food consumption. Study 1 found that “wanting,” hunger, and consumption were greater in the cue-rich compared to neutral laboratory, while “liking” did not differ between conditions. This study provides support for the incentive-sensitization theory as applied to eating behavior. Study 2 developed and tested a novel paradigm for identifying two phenotypes of cue-responsivity, sign-tracking and goal-tracking. Children aged 5-7 (n = 64) engaged in a Pavlovian conditioning task designed to assess propensity to engage with a cue (sign-tracking) versus the location of a reward (goal-tracking). Children then engaged in tasks assessing food motivation and inhibitory control. Contrary to hypotheses, Study 1 did not find a distinct goal-tracking phenotype, and did not find sign-tracking behavior to be associated with either food motivation or inhibitory control. Considerations for how to examine these phenotypes in future research are discussed. Study 3 examined how resting state functional connectivity (rsFC) relates to obesity, food consumption, food motivation, and inhibitory control in adolescents (n = 164) aged 13-16 who ranged from lean to obese. Participants completed tasks assessing food motivation and inhibitory control, then on a second visit underwent a resting-state scan and then completed a food consumption task in a cue-rich environment. Obesity and elevated food motivation were found to be marked by altered connectivity in areas in the salience network (e.g., caudate, NAcc, OFC) and the default mode network (e.g., PCC, hippocampus). However, obesity was not found to be associated with behavioral outcomes, thus these behaviors were not found to mediate associations between obesity and rsFC patterns. These findings provide suggestions as to effective prevention and intervention targets. The current dissertation provides evidence for a strong role of elevated food motivation (especially in the context of food cues) in the overconsumption of palatable foods. Clinical implications and suggestions for intervention are discussed.