Decision-Making Scores and Hunger Susceptibility: A Positive Correlation Mediated by Fasting FGF21 Independently of Body Fat

Background/Objectives: Understanding the relationship between metabolism and eating behavior may improve how we treat and prevent obesity. Fibroblast growth factor 21 (FGF21) is a hormone secreted by the liver with a putative role in energy expenditure, energy intake, and weight regulation. In this secondary analysis, we studied how fasting FGF21 is correlated with eating behavior and decision making, as measured by the Three-Factor Eating Questionnaire (TFEQ) and the Iowa Gambling Task (IGT), respectively. Methods: Participants (n = 98; women = 19; white = 31) were medically healthy, between 18 and 55 years of age, weight-stable 6 months before admission, and had normal glucose regulation. Women were premenopausal and not pregnant. Pearson partial correlations were determined, accounting for age, sex, and body fat percentage. A mediation analysis examining whether the association between hunger and IGT score was mediated by FGF21 values was performed using general linear models. Results: In partial correlations adjusted for age, sex, and body fat percentage, we found that fasting FGF21 concentrations were positively correlated with hunger susceptibility (sum of internal and external cues) (partial r = 0.26, p = 0.02) and internal hunger (partial r = 0.22, p = 0.04), disinhibition (partial r = 0.27, p = 0.01), and better decision making (higher IGT scores) (partial r = 0.40, p = 0.0001). We also found a correlation between hunger susceptibility and better decision making, including the same covariates (partial r = 0.25, p = 0.03). However, this correlation was mediated (36%) by fasting FGF21. Conclusions: In this study, participants with greater susceptibility to hunger cues had higher IGT scores (better decision making) in the setting of higher fasting FGF21 concentrations. This provides further evidence of the role of FGF21 in the interplay between eating behavior and decision making. Further studying this topic may improve our understanding of the complex relationship between assessing energy requirements and cognitive processes related to eating behavior.