Dynamic heartbeat tracking beyond the laboratory: Introducing the novel Graz Ambulatory Interoception Task (GRAIT)

Acute fasting modulates autonomic nervous system function and ambulatory cardiac interoception

Intermittent fasting has been associated with diverse physical and psychological health benefits. According to previous research, fasting-induced alterations in psychophysiological functioning should facilitate the accurate detection of an internal bodily signal (like the heart), which is referred to as interoceptive accuracy. In two within-subjects studies we aimed to examine whether an intermittent fasting protocol (i) evokes distinct autonomic nervous system changes in the laboratory and (ii) improves (objectifiable) interoceptive accuracy and sensibility (i.e., the subjective belief in perceiving bodily signals) in everyday life. Study 1 (N = 36) found increasing heart rate variability (precisely, the root mean square of successive differences; RMSSD) accompanied by a more vascular than myocardial response following a 16 h fast. Study 2 (N = 40) applied an ecological momentary assessment design including intermittent fasting (8 h normal eating followed by 16 h fasting) and normal eating (24 h normal eating) for three consecutive days each. Findings suggested a tendency toward higher interoceptive accuracy and sensibility during the fasting regimen, which was particularly pronounced in individuals exhibiting lower RMSSD. Together, findings suggest that (short-term) fasting seems to facilitate momentary attention to organismic cues due to alterations in autonomic nervous system function.

The misjudgment of interoceptive awareness: Systematic overrating of interoceptive awareness among individuals with lower interoceptive metacognitive skills

Knowing when perceiving inner bodily signals better and when perceiving them worse is a health relevant but understudied dimension of interoception. Therefore, the present study assessed interoceptive metacognition (IMC) as the skill to adequately monitor interoceptive accuracy in the cardiac domain. We used the Graz Ambulatory Interoception task (GRAIT), which applied two intervals of the heartbeat tracking task 12 times a day for 3 days in total to n = 66 participants. We assessed IMC as the relative correspondence between interoceptive accuracy and the subjective confidence ratings. We found that 6 % of the total IMC variance was due to person, which was assessed reliable (RKRn=0.81). Furthermore, the between-person variation of IMC was negatively associated with the MAIA (especially attention regulation and self-regulation). People who believe that they are aware of their interoceptive experiences (MAIA) showed lower IMC. This study advocates the assessment of interoception in everyday life.