Laura L. Wilkinson

Computer-based assessments of expected satiety predict behavioural measures of portion-size selection and food intake ☆

Previously, expected satiety (ES) has been measured using software and two-dimensional pictures presented on a computer screen. In this context, ES is an excellent predictor of self-selected portions, when quantified using similar images and similar software. In the present study we sought to establish the veracity of ES as a predictor of behaviours associated with real foods. Participants (N=30) used computer software to assess their ES and ideal portion of three familiar foods. A real bowl of one food (pasta and sauce) was then presented and participants self-selected an ideal portion size. They then consumed the portion ad libitum. Additional measures of appetite, expected and actual liking, novelty, and reward, were also taken. Importantly, our screen-based measures of expected satiety and ideal portion size were both significantly related to intake (p<.05). By contrast, measures of liking were relatively poor predictors (p>.05). In addition, consistent with previous studies, the majority (90%) of participants engaged in plate cleaning. Of these, 29.6% consumed more when prompted by the experimenter. Together, these findings further validate the use of screen-based measures to explore determinants of portion-size selection and energy intake in humans.

Episodic Memory and Appetite Regulation in Humans

Psychological and neurobiological evidence implicates hippocampal-dependent memory processes in the control of hunger and food intake. In humans, these have been revealed in the hyperphagia that is associated with amnesia. However, it remains unclear whether ‘memory for recent eating’ plays a significant role in neurologically intact humans. In this study we isolated the extent to which memory for a recently consumed meal influences hunger and fullness over a three-hour period. Before lunch, half of our volunteers were shown 300 ml of soup and half were shown 500 ml. Orthogonal to this, half consumed 300 ml and half consumed 500 ml. This process yielded four separate groups (25 volunteers in each). Independent manipulation of the ‘actual’ and ‘perceived’ soup portion was achieved using a computer-controlled peristaltic pump. This was designed to either refill or draw soup from a soup bowl in a covert manner. Immediately after lunch, self-reported hunger was influenced by the actual and not the perceived amount of soup consumed. However, two and three hours after meal termination this pattern was reversed - hunger was predicted by the perceived amount and not the actual amount. Participants who thought they had consumed the larger 500-ml portion reported significantly less hunger. This was also associated with an increase in the ‘expected satiation’ of the soup 24-hours later. For the first time, this manipulation exposes the independent and important contribution of memory processes to satiety. Opportunities exist to capitalise on this finding to reduce energy intake in humans.

Attachment anxiety, disinhibited eating, and body mass index in adulthood

Several studies report a relationship between body mass index (BMI) and disinhibited eating (a failure to restrict intake and to overeat). However, the aetiology of disinhibited eating has received scant attention. In this study, we consider a role for ‘attachment orientation’, a trait that reflects the quality of bonding in early life and remains stable throughout adulthood. Participants (N=200, females=135, BMI range from 17.4 to 41.1 kg m−2) completed measures of disinhibition and attachment orientation. ‘Attachment anxiety’ was a good predictor of disinhibited eating (P<0.001). Furthermore, mediation analysis confirmed that it is through this relationship that attachment anxiety also predicts BMI (P=0.02). These findings are consistent with other studies, showing an association between attachment orientation and other disinhibited behaviours, including alcohol and substance abuse. Our interpretation is that disinhibited eaters engage in external affect regulation. In doing so, they seek to mitigate the anxiety associated with poor interpersonal attachments.

Conditioning 'fullness expectations' in a novel dessert.

Calorie-for-calorie, foods differ considerably in the extent to which they are expected to deliver satiation. We sought to demonstrate that flavour-nutrient learning modifies these expectations. On day 1, participants (N=56) tasted a novel dessert and then completed a measure of expected satiation. Participants then consumed either a low (228 kcal) or high (568 kcal) energy-dense dessert (sensory characteristics matched). On day 2, expected satiation was assessed and then intake was measured using an intermediate energy-dense dessert. Expected satiation did increase but only in the high energy-dense condition (17.4%). This difference was not reflected in a measure of intake.

Eating me up inside: Priming attachment security and anxiety, and their effects on snacking

Recent research has shown that attachment anxiety (a model of interpersonal relationships characterised by a fear of abandonment) is a good predictor of disinhibited eating and, in turn, body mass index. However, this association has yet to be explored within an eating episode. The present study investigated the effect of priming attachment security and attachment anxiety on food intake. Normal weight participants (N = 21) were primed with security and anxiety on separate occasions and given ad libitum access to a snack food. Priming anxiety led to a significantly higher food intake than priming security (p = .016). We suggest that participants consumed more food in response to the anxious prime in an attempt to manage the resulting feelings of insecurity. These results provide behavioural evidence for a link between attachment anxiety and disinhibited eating.

Presenting a food in multiple smaller units increases expected satiety

Presentation of the same amount of a food in multiple smaller units (‘segmentation’) has been shown to reduce food intake and increase estimates of the amount of food consumed. However, this effect has been demonstrated for ad libitum food intake only. In the majority of cases, meals are not consumed ad libitum, but are pre-selected and consumed in their entirety, Expected satiety (ES; the anticipated capacity of a portion of food to relieve hunger between meals) is an excellent predictor of portion size selection. This study tested the hypothesis that segmentation increases ES. It was also hypothesised that perceived volume (PV) may account for the relationship between segmentation and ES. Sixty-eight participants made computer-based ES and PV judgments for equicaloric portions of three test foods (salted peanuts, spaghetti Bolognese, and chicken tikka masala), which were presented in either a single unit or as multiple smaller units (three or six units). Results revealed a consistent effect of segmentation on ES - foods presented in multiple smaller units were expected to deliver significantly greater satiety than when presented in a single unit (p < 0.005). Furthermore, results indicated that the effect of segmentation on ES was attributable to an increase in PV. ES plays an important role in determining the portion sizes that people select. Therefore, awareness of the effect of segmentation on ES may help to inform the design of foods that confer benefits for healthy weight maintenance.

Disinhibited eating mediates differences in attachment insecurity between bariatric surgery candidates/recipients and lean controls

Previous research has shown that attachment anxiety is a good predictor of body mass index. This relationship is significantly mediated by disinhibited (over-) eating and is likely to reflect a specific form of affect regulation. This study explored whether obese bariatric surgery candidates (BSC; N=34) and bariatric surgery recipients (BSR; N=15) would show higher levels of attachment insecurity (higher attachment anxiety and/or higher attachment avoidance) than a group of age and gender-matched lean controls (N=54). Mediation analyses showed that compared to lean controls (M=2.96, SE=0.1), both BSC (M=3.5, SE=0.2) and BSR (M=3.4, SE=0.2) groups had a more insecure attachment orientation. These relationships were significantly mediated by disinhibited eating (BSC: lower limit confidence interval (LLCI)=0.06 and upper limit confidence interval (ULCI)=0.62; BSR: LLCI=0.02 and ULCI=0.76). There was no such relationship when the BSC and BSR groups were compared (LLCI=−0.15 & ULCI=0.3). These observations suggest that attachment insecurity may be a risk factor for obesity and bariatric surgery because of associated disinhibited eating. Moreover, these factors may be important to consider when bariatric surgery results in poor outcomes.

Keeping Pace with Your Eating: Visual Feedback Affects Eating Rate in Humans

Deliberately eating at a slower pace promotes satiation and eating quickly has been associated with a higher body mass index. Therefore, understanding factors that affect eating rate should be given high priority. Eating rate is affected by the physical/textural properties of a food, by motivational state, and by portion size and palatability. This study explored the prospect that eating rate is also influenced by a hitherto unexplored cognitive process that uses ongoing perceptual estimates of the volume of food remaining in a container to adjust intake during a meal. A 2 (amount seen; 300ml or 500ml) x 2 (amount eaten; 300ml or 500ml) between-subjects design was employed (10 participants in each condition). In two ‘congruent’ conditions, the same amount was seen at the outset and then subsequently consumed (300ml or 500ml). To dissociate visual feedback of portion size and actual amount consumed, food was covertly added or removed from a bowl using a peristaltic pump. This created two additional ‘incongruent’ conditions, in which 300ml was seen but 500ml was eaten or vice versa. We repeated these conditions using a savoury soup and a sweet dessert. Eating rate (ml per second) was assessed during lunch. After lunch we assessed fullness over a 60-minute period. In the congruent conditions, eating rate was unaffected by the actual volume of food that was consumed (300ml or 500ml). By contrast, we observed a marked difference across the incongruent conditions. Specifically, participants who saw 300ml but actually consumed 500ml ate at a faster rate than participants who saw 500ml but actually consumed 300ml. Participants were unaware that their portion size had been manipulated. Nevertheless, when it disappeared faster or slower than anticipated they adjusted their rate of eating accordingly. This suggests that the control of eating rate involves visual feedback and is not a simple reflexive response to orosensory stimulation.

Attachment anxiety, disinhibited eating and body mass index in adulthood

Several studies report a relationship between body mass index (BMI) and disinhibited eating (a failure to restrict intake and to overeat). However, the aetiology of disinhibited eating has received scant attention. In this study, we consider a role for ‘attachment orientation’, a trait that reflects the quality of bonding in early life and remains stable throughout adulthood. Participants (N1⁄4200, females1⁄4135, BMI range from 17.4 to 41.1 kg m ) completed measures of disinhibition and attachment orientation. ‘Attachment anxiety’ was a good predictor of disinhibited eating (Po0.001). Furthermore, mediation analysis confirmed that it is through this relationship that attachment anxiety also predicts BMI (P1⁄40.02). These findings are consistent with other studies, showing an association between attachment orientation and other disinhibited behaviours, including alcohol and substance abuse. Our interpretation is that disinhibited eaters engage in external affect regulation. In doing so, they seek to mitigate the anxiety associated with poor interpersonal attachments. International Journal of Obesity (2010) 34, 1442–1445; doi:10.1038/ijo.2010.72; published online 30 March 2010