The role of interoception in age-related obesity: A structural equation modelling study.

The obesity pandemic and its adverse effect on health and quality of life are well established. In younger populations, interoception and aberrant eating behaviour contribute to overconsumption and being overweight. Although the incidence of obesity is higher in older individuals, they remain under-researched in the obesity literature. Therefore, the present study considered the role of general (interoceptive sensibility) and appetite-specific (hunger drive and satiety responsiveness) interoception and obesogenic eating behaviour (food responsivity, emotional eating, enjoyment of eating) in the association between age and BMI. A total of 1006 female adults (aged 18 to 80) completed the Adult Eating Behaviour Questionnaire and the Interoceptive Attention and Accuracy scales. Structural Equation Modelling (SEM) in AMOS was used to explore the data for multiple serial mediation effects. Despite being more overweight, older adults reported lower interoceptive attention, hunger drive, emotional overeating, food responsivity, and enjoyment of food. In contrast, compared to younger adults, older adults reported a higher interoceptive accuracy, and a similar responsivity to satiety. Importantly, two indirect pathways positively mediated the link between age and BMI: (1) age ➤(-)➤ interoceptive attention ➤(+)➤ satiety responsivity ➤(-)➤ emotional eating ➤(+)➤ BMI and (2) age ➤(-)➤ interoceptive attention ➤(+)➤ satiety responsivity ➤(-)➤ food responsivity ➤(+)➤ BMI. However, a stronger antagonistic indirect pathway was also present: age ➤(-)➤ interoceptive attention ➤(+)➤ hunger drive ➤(+)➤ emotional eating ➤(+)➤ BMI. The present findings suggested that overall reduced interoceptive attention in older adults may protect against weight gain by lowering hunger and the propensity towards obesogenic eating behaviours. These findings have implications for the design of appetite interventions in older populations.

Carbohydrate and sleep: An evaluation of putative mechanisms.

Sleep problems are extremely common in industrialized countries and the possibility that diet might be used to improve sleep has been considered. The topic has been reviewed many times, resulting in the frequent suggestion that carbohydrate increases the uptake of tryptophan by the brain, where it is metabolized into serotonin and melatonin, with the suggestion that this improves sleep. An alternative mechanism was proposed based on animal literature that has been largely ignored by those considering diet and sleep. The hypothesis was that, as in the hypothalamus there are glucose-sensing neurons associated with the sleep-wake cycle, we should consider the impact of carbohydrate-induced changes in the level of blood glucose. A meta-analysis found that after consuming a lower amount of carbohydrate, more time was spent in slow-wave sleep (SWS) and less in rapid-eye-movement sleep. As the credibility of alternative mechanisms has tended not to have been critically evaluated, they were considered by examining their biochemical, nutritional, and pharmacological plausibility. Although high carbohydrate consumption can increase the uptake of tryptophan by the brain, it only occurs with such low levels of protein that the mechanism is not relevant to a normal diet. After entering the brain tryptophan is converted to serotonin, a neurotransmitter known to influence so many different aspects of sleep and wakefulness, that it is not reasonable to expect a uniform improvement in sleep. Some serotonin is converted to melatonin, although the exogenous dose of melatonin needed to influence sleep cannot be credibly provided by the diet. This review was registered in the International Prospective Register of Systematic Reviews (CRD42020223560).

Individual differences in sensory and expectation driven interoceptive processes: a novel paradigm with implications for alexithymia, disordered eating and obesity.

Those with disordered eating and/or obesity often express difficulties in sensing or interpreting what is happening in the body (interoception). However, research is hindered by conceptual confusion, concerns surrounding domain specificity, and an inability to distinguish sensory (bottom-up) and expectation driven (top-down) interoceptive processes. A paradigm was therefore developed from an active inference perspective. Novel indices were computed and examined in those with alexithymia: a personality associated with interoceptive deficits and disordered eating. The paradigm successfully identified individuals driven by sensations rather than expectations: alexithymia was characterized by attenuated prior precision (a larger divergence between pre-prandial and post-prandial satiety, and low expectation confidence), and increased prediction error (a higher correlation between changes in hunger and blood glucose, and greater rebound hunger after a sensory incongruent drink). In addition, those with a higher BMI were less confident and had a larger anticipated satiety divergence. These findings demonstrate the need to move beyond existing paradigms such as the Satiety Quotient and Heartbeat Counting Task which may have limited our understanding of eating behaviour.

Interoceptive accuracy moderates the response to a glucose load: a test of the predictive coding framework.

Recently, interoception and homeostasis have been described in terms of predictive coding and active inference. Afferent signals update prior predictions about the state of the body, and stimulate the autonomic mediation of homeostasis. Performance on tests of interoceptive accuracy (IAc) may indicate an individual's ability to assign precision to interoceptive signals, thus determining the relative influence of ascending signals and the descending prior predictions. Accordingly, individuals with high IAc should be better able to regulate during the postprandial period. One hundred females were allocated to consume glucose, an artificially sweetened drink, water or no drink. Before, and 30 min after a drink, IAc, heart rate (HR) and blood glucose (BG) were measured, and participants rated their hunger, thirst and mood. A higher IAc was related to lower BG levels, a decline in anxiety and a higher HR, after consuming glucose. A higher IAc also resulted in a larger decline in hunger if they consumed either glucose or sucralose. These data support the role of active inference in interoception and homeostasis, and suggest that the ability to attend to interoceptive signals may be critical to the maintenance of physical and emotional health.