Dietary restraint and stress-induced alterations in eating: Exploring the role of heart rate variability as a proxy for self-regulation, attentional bias, and perceived safety
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Restraint theory posits that the capacity to successfully diet is cognitively demanding, requiring exertion of cognitive control over eating. Demands that deplete this limited inner resource (e.g., stress) can thus lead restrained eaters to become disinhibited and consume large amounts of food. This program of research aimed to objectively investigate the causal role of self-regulation in restrained eaters’ disinhibition. As a robust literature indicates that higher heart rate variability (HRV) indexes self-regulatory capacity, HRV was used to quantify changes in self-regulation. Study One explored whether HRV mediated disinhibition in 93 female undergraduates exposed to a laboratory stressor and subsequent bogus taste test. Though HRV significantly mediated the link between the stressor and food intake, the stress-induced reduction in HRV was associated with decreased intake. Dietary restraint also moderated the pathway between HRV and intake, such that the indirect effect of stress on intake via HRV was only significant for less restrained eaters, but restrained eaters did not show evidence of disinhibition. In a subsequent study of 147 females, Study Two examined whether a serial mediation via HRV and attentional bias to food accounted for these unexpected findings. It was predicted low HRV may attenuate attentional bias to food and reduce intake in less restrained eaters while it would enhance attentional bias to food and intake in more restrained eaters. It was further posited that the model would only emerge for those uncertain about safety from additional stress. None of the hypotheses were supported. However, an exploratory moderated serial mediation revealed sympathetic nervous system activity led to a significant reduction in hunger that attenuated intake for less restrained eaters uncertain about their safety. Although hunger among more restrained eaters similarly decreased, they did not reduce their intake. Overall, these findings imply restrained eaters show a disconnect from internal physiological cues that may facilitate disordered eating when stressed.