Eat now or later: self-control as an overlapping cognitive mechanism of depression and obesity

While overlapping neurobiological mechanisms are known, relatively little is known about how "self-control" and cognitive affective processing of rewards may also influence the bi-directional risk between obesity and depression. The objective of this study was to identify the extent to which "self-control," measured using a delay discounting task is co-related to BMI and Depression diagnostic thresholds. A within-subjects counterbalanced design was used in which 92 participants (Mean ± SD: BMI = 27.9 ± 3.5, HAMD = 14.7 ± 7.7) completed a series of clinical diagnostic, survey, and demographic questionnaires in a behavioral health laboratory setting. For the delay discounting task, participants chose between one large delayed reward and one successively smaller immediate reward for four food types (dessert, fried food, fruit, and vegetable). Results showed that delay discounting scores were predictive of BMI and depression with lower delay discounting scores associated with higher BMI and HAMD for the dessert (HAMD scores (β = -.197, p = .013), BMI (β = -.239, p < .001)) and fried food (HAMD scores (β = -.328, p = .001), BMI (β = -.166, p = .027)). Clinical significance was further evident when HAMD and BMI scores were converted to diagnostic thresholds. Only depression and/or atypical depressive symptoms were related to delay discounting scores with the fruit and vegetable. Thus, reduced cognitive affective self-control for impulsive food choices-particularly for "comfort foods" high in fat and sugar-appears to be a shared cognitive mechanism for both conditions perhaps contributing to the high prevalence of co-morbid mood disorders and weight gain.