Increased brain and behavioural susceptibility to portion size in children with loss of control eating.

BACKGROUND: Portion size influences intake (i.e. the portion size effect [PSE]), yet determinants of susceptibility to the PSE are unclear. OBJECTIVE: We tested whether children who reported an episode of loss of control (LOC) eating over the last 3 months would be more susceptible to the PSE and would show differential brain responses to food cues compared with children with no-LOC. METHODS: Across five sessions, children (n = 47; 7-10 years) consumed four test meals at 100%, 133%, 167% and 200% conditions for portion size and completed a functional magnetic resonance imaging scan while viewing pictures of foods varied by portion size and energy density (ED). Incidence of LOC over the past 3 months was self-reported. Random coefficient models were tested for differences in the shape of the PSE curve by LOC status. A whole-brain analysis was conducted to determine response to food cues during the functional magnetic resonance imaging. RESULTS: Reported LOC (n = 13) compared with no-LOC (n = 34) was associated with increased susceptibility to the PSE, as evidenced by a positive association with the linear slope (P < 0.005), and negative association with the quadratic slope (P < 0.05) of the intake curve. Children who reported LOC compared with no-LOC showed increased activation in the left cerebellum to small relative to large portions (P < 0.01) and right cerebellum to High-ED relative to Low-ED food cues (P < 0.01). CONCLUSION: Children who reported LOC were more susceptible to the PSE and showed alterations in food-cue processing in the cerebellum, a hindbrain region implicated in satiety signalling.

Reduced neural responses to food cues might contribute to the anorexigenic effect of acute exercise observed in obese but not lean adolescents.

Acute exercise has been found to reduce subsequent energy intake in obese adolescents. Although it has been suggested that some neural pathways are involved in this post-exercise energy intake regulation, it remains unknown whether the post-exercise attentional response to food cues differs as a function of weight status. We hypothesize that there will be a reduction in the neural response to food cues as a result of exercise in obese adolescents, but not in their lean counterparts. Fourteen obese and 14 lean adolescent boys (12-15 years) were randomized (within-subjects design) to remain seated (CON) or to exercise 45 minutes at 65% of their maximal capacities (EX). After the exercise or sitting period, the adolescents' cognitive engagement in the processing of food vs. non-food cues was assessed during an attentional computer-based task with electroencephalography (EEG) recording. An ad libitum lunch meal was offered and appetite feelings were assessed (visual analog scales). There was no main effect of condition on energy intake in lean subjects, but obese adolescents ate significantly less following EX compared with CON (P<.05). There was no effect of condition or stimulus type (food vs. non-food) on the EEG-recorded amplitude of the P3b component in lean adolescents. However, the response to food cues was significantly reduced compared with non-food stimuli after exercise in obese participants (P<.01). Following EX, but not CON, total body weight, body mass index, and fat mass were inversely correlated with the EEG response to food-non-food stimuli (all P<.05). However, this response was not associated with ad libitum EI (both P>.1). Acute exercise favors decreased neural response to food cues compared with non-food cues in obese but not lean adolescents, suggesting differential effects of exercise on the neural processing of food cues based on weight status.

Brain regions implicated in inhibitory control and appetite regulation are activated in response to food portion size and energy density in children.

OBJECTIVE: Large portions of energy-dense foods drive energy intake but the brain mechanisms underlying this effect are not clear. Our main objective was to investigate brain function in response to food images varied by portion size (PS) and energy density (ED) in children using functional magnetic resonance imaging (fMRI). METHODS AND DESIGN: Blood-oxygen-level-dependent (BOLD) fMRI was completed in 36 children (ages 7-10 years) after a 2-h fast while viewing food images at two levels of PS (Large PS, Small PS) and two levels of ED (High ED, Low ED). Children rated perceived fullness pre- and post-fMRI, as well as liking of images on visual analog scales post-fMRI. Anthropometrics were completed 4 weeks before the fMRI. Large PS vs Small PS and High ED vs Low ED were compared with region-of-interest analyses using Brain Voyager v 2.8. RESULTS: Region-of-interest analyses revealed that activation in the right inferior frontal gyrus (P=0.03) was greater for Large PS vs Small PS. Activation was reduced for High ED vs Low ED in the left hypothalamus (P=0.03). Main effects were no longer significant after adjustment for pre-fMRI fullness and liking ratings (PS, P=0.92; ED, P=0.58). CONCLUSION: This is the first fMRI study to report increased activation to large portions in a brain region that is involved in inhibitory control. These findings may contribute to understanding why some children overeat when presented with large portions of palatable food.

Reduced neural response to food cues following exercise is accompanied by decreased energy intake in obese adolescents.

BACKGROUND: Acute exercise has been found to favor a transient anorexigenic effect in obese adolescents. Although the role of some gastro-peptides has been suggested as an explanation for this observed reduced energy intake after exercise, it is unknown whether neural pathways involved in the regulation of food intake are modulated in youth. METHODS: Body composition (dual-energy X-ray absorptiometry) and aerobic capacities were assessed in 19 obese adolescent boys. Participants were randomized to remain at rest in a sitting position (CON condition) or to exercise 45 min at 65% of their maximal capacities (EX condition) by the end of the morning. An attentional computer task with electroencephalography recording was completed immediately after the exercise or sitting period to measure an event-related component (P3b) reflecting the level of cognitive engagement in the processing of food cues. A lunch test-meal was offered ad libitum and appetite feelings assessed at regular intervals using visual analog scales. RESULTS: The 45-min cycling exercise set at 65% VO2max induced a mean energy expenditure of 399±75 kcal. Both absolute (P<0.05) and relative (P<0.001) subsequent energy intake were significantly reduced after EX (1037±260 and 639±256 kcal, respectively) compared with CON (1116±243 and 1011±239 kcal, respectively). The energy ingested derived from each macronutrient and self-reported appetite remained unchanged. Although the amplitudes of the P3b component evoked by food and non-food visual stimuli were not significantly different during CON, the response to food cues was significantly reduced compared with non-food stimuli after exercise (P<0.01). DISCUSSION: An acute exercise favors decreased neural response to food cues compared with non-food ones in obese adolescents that may contribute to their subsequently reduced energy intake.