Visual Food Research Articles

The effects of a single bout of aerobic or resistance exercise on food reward

It is unknown whether an acute bout of calorie-matched aerobic and resistance exercise alters food reward in a similar manner. Thus, we examined the effects of isocaloric resistance and aerobic exercise sessions on acute food reward. Sixteen men and women (age: 21.9 ± 2.6 years; BMI: 22.8 ± 1.8 kg/m2) participated in three randomized crossover sessions: aerobic exercise, resistance exercise, and sedentary control. The target exercise energy expenditure was matched at 4 kcal/kg of body weight, and performed at 70% of VO2peak or 12 repetition-maximum (equivalent to 70% of 1 repetition-maximum). A validated computer task assessed the wanting and liking for visual food cues following exercise, and following an ad libitum lunch. Decreases in the relative preference for high vs. low fat foods were noted following exercise compared to the control session, and this was independent of modality (aerobic: P = 0.04; resistance: P = 0.03). Furthermore, the explicit liking for high vs. low fat foods was lower following resistance exercise compared to the control session (P = 0.04). However, these changes in food reward were not correlated with changes in energy intake (EI) between sessions. Exercise, independent of modality, led to decreases in the relative preference for high fat relative to low fat foods. Additionally, decreases in the hedonic “liking” of high fat foods following resistance, but not aerobic, exercise may imply that modality does influence acute food hedonic responses. However, these decreases in food hedonics were not related to lower EI, thus suggesting that a dissociation may exist between food hedonics and actual EI.

Attentional bias to food-related visual cues: is there a role in obesity?

The incentive sensitisation model of obesity suggests that modification of the dopaminergic associated reward systems in the brain may result in increased awareness of food-related visual cues present in the current food environment. Having a heightened awareness of these visual food cues may impact on food choices and eating behaviours with those being most aware of or demonstrating greater attention to food-related stimuli potentially being at greater risk of overeating and subsequent weight gain. To date, research related to attentional responses to visual food cues has been both limited and conflicting. Such inconsistent findings may in part be explained by the use of different methodological approaches to measure attentional bias and the impact of other factors such as hunger levels, energy density of visual food cues and individual eating style traits that may influence visual attention to food-related cues outside of weight status alone. This review examines the various methodologies employed to measure attentional bias with a particular focus on the role that attentional processing of food-related visual cues may have in obesity. Based on the findings of this review, it appears that it may be too early to clarify the role visual attention to food-related cues may have in obesity. Results however highlight the importance of considering the most appropriate methodology to use when measuring attentional bias and the characteristics of the study populations targeted while interpreting results to date and in designing future studies.

Toward a new computer-based and easy-to-use tool for the objective measurement of motivational states in humans: a pilot study

The experimental methods currently used for assessing motivational processes in humans have two major limitations. Some of them rely on global subjective assessments while others evaluate these processes using food-related tasks often coupled with functional neuroimaging techniques that have however limited availability and important associated costs. Here we propose a novel experimental computer-generated and easy-to-use tool primarily based on the presentation of food images and designed to provide a quantitative and objective measurement of motivational states in humans. Two tasks evaluating respectively visual and time discrimination capacities were developed and tested on a sample of 30 healthy subjects. The subjects were asked to compare a food stimulus (food picture in color) and its devalued counterpart (same image in grayscale), at each trial, assessing either the size (task A) or the duration of presentation (task B). Geometric figures presented in color or grayscale were used as controls. The subjects were invited to perform tasks A and B during three separate experimental sessions, one under fasting and two under satiety. Relative to their devalued counterparts, the food images were judged significantly greater in size and shorter in time of presentation in fasting than in satiety. In fasting, the size and the time of presentation for the food images were respectively estimated significantly greater and shorter than for the control images when compared to their respective devalued counterparts. Conversely, there was no overall change in the perception of size or duration of presentation for the control images between fasting and satiety conditions. Our findings support that hunger specifically affects the perception of visual food stimuli, and suggest that this novel computer-based test is potentially useful for the study of motivational states in human diseases that are characterized by serious disturbances in reward processing.

Obesity-associated melanocortin-4 receptor mutations are associated with changes in the brain response to food cues.

Context:Mutations in the melanocortin-4 receptor (MC4R) represent the commonest genetic form of obesity and are associated with hyperphagia.Objective:The aim of this study was to investigate whether melanocortin signaling modulates anticipatory food reward by studying the brain activation response to food cues in individuals with MC4R mutations.Design/Setting/Participants/Main Outcome Measure:We used functional magnetic resonance imaging to measure blood oxygen level-dependent responses to images of highly palatable, appetizing foods, bland foods, and non-food objects in eight obese individuals with MC4R mutations, 10 equally obese controls, and eight lean controls with normal MC4R genotypes. Based on previous evidence, we performed a region-of-interest analysis centered on the caudate/putamen (dorsal striatum) and ventral striatum.Results:Compared to non-foods, appetizing foods were associated with activation in the dorsal and ventral striatum in lean controls and in MC4R-deficient individuals. Surprisingly, we observed reduced activation of the dorsal and ventral striatum in obese controls relative to MC4R-deficient patients and lean controls. There were no group differences for the contrast of disgusting foods with bland foods or non-foods, suggesting that the effects observed in response to appetizing foods were not related to arousal.Conclusion:We identified differences in the striatal response to food cues between two groups of obese individuals, those with and those without MC4R mutations. These findings are consistent with a role for central melanocortinergic circuits in the neural response to visual food cues.

Neural responses to visual food cues according to weight status: a systematic review of functional magnetic resonance imaging studies.

Emerging evidence from recent neuroimaging studies suggests that specific food-related behaviors contribute to the development of obesity. The aim of this review was to report the neural responses to visual food cues, as assessed by functional magnetic resonance imaging (fMRI), in humans of differing weight status. Published studies to 2014 were retrieved and included if they used visual food cues, studied humans >18 years old, reported weight status, and included fMRI outcomes. Sixty studies were identified that investigated the neural responses of healthy weight participants (n = 26), healthy weight compared to obese participants (n = 17), and weight-loss interventions (n = 12). High-calorie food images were used in the majority of studies (n = 36), however, image selection justification was only provided in 19 studies. Obese individuals had increased activation of reward-related brain areas including the insula and orbitofrontal cortex in response to visual food cues compared to healthy weight individuals, and this was particularly evident in response to energy dense cues. Additionally, obese individuals were more responsive to food images when satiated. Meta-analysis of changes in neural activation post-weight loss revealed small areas of convergence across studies in brain areas related to emotion, memory, and learning, including the cingulate gyrus, lentiform nucleus, and precuneus. Differential activation patterns to visual food cues were observed between obese, healthy weight, and weight-loss populations. Future studies require standardization of nutrition variables and fMRI outcomes to enable more direct comparisons between studies.

Human protein status modulates brain reward responses to food cues

Protein is indispensable in the human diet, and its intake appears tightly regulated. The role of sensory attributes of foods in protein intake regulation is far from clear. We investigated the effect of human protein status on neural responses to different food cues with the use of functional magnetic resonance imaging (fMRI). The food cues varied by taste category (sweet compared with savory) and protein content (low compared with high). In addition, food preferences and intakes were measured. We used a randomized crossover design whereby 23 healthy women [mean ± SD age: 22 ± 2 y; mean ± SD body mass index (in kg/m(2)): 22.5 ± 1.8] followed two 16-d fully controlled dietary interventions involving consumption of either a low-protein diet (0.6 g protein · kg body weight(-1) · d(-1), ~7% of energy derived from protein, approximately half the normal protein intake) or a high-protein diet (2.2 g protein · kg body weight(-1) · d(-1), ~25% of energy, approximately twice the normal intake). On the last day of the interventions, blood oxygen level-dependent (BOLD) responses to odor and visual food cues were measured by using fMRI. The 2 interventions were followed by a 1-d ad libitum phase, during which a large array of food items was available and preference and intake were measured. When exposed to food cues (relative to the control condition), the BOLD response was higher in reward-related areas (orbitofrontal cortex, striatum) in a low-protein state than in a high-protein state. Specifically, BOLD was higher in the inferior orbitofrontal cortex in response to savory food cues. In contrast, the protein content of the food cues did not modulate the BOLD response. A low protein state also increased preferences for savory food cues and increased protein intake in the ad libitum phase as compared with a high-protein state. Protein status modulates brain responses in reward regions to savory food cues. These novel findings suggest that dietary protein status affects taste category preferences, which could play an important role in the regulation of protein intake in humans. This trial was registered at www.trialregister.nl/trialreg/admin/rctview.asp?TC=3288 as NTR3288.

Food-pics: an image database for experimental research on eating and appetite

Our current environment is characterized by the omnipresence of food cues. The sight and smell of real foods, but also graphically depictions of appetizing foods, can guide our eating behavior, for example, by eliciting food craving and influencing food choice. The relevance of visual food cues on human information processing has been demonstrated by a growing body of studies employing food images across the disciplines of psychology, medicine, and neuroscience. However, currently used food image sets vary considerably across laboratories and image characteristics (contrast, brightness, etc.) and food composition (calories, macronutrients, etc.) are often unspecified. These factors might have contributed to some of the inconsistencies of this research. To remedy this, we developed food-pics, a picture database comprising 568 food images and 315 non-food images along with detailed meta-data. A total of N = 1988 individuals with large variance in age and weight from German speaking countries and North America provided normative ratings of valence, arousal, palatability, desire to eat, recognizability and visual complexity. Furthermore, data on macronutrients (g), energy density (kcal), and physical image characteristics (color composition, contrast, brightness, size, complexity) are provided. The food-pics image database is freely available under the creative commons license with the hope that the set will facilitate standardization and comparability across studies and advance experimental research on the determinants of eating behavior.

Sexually dimorphic functional connectivity in response to high vs. low energy-dense food cues in obese humans: An fMRI study

Sexually-dimorphic behavioral and biological aspects of human eating have been described. Using psychophysiological interaction (PPI) analysis, we investigated sex-based differences in functional connectivity with a key emotion-processing region (amygdala, AMG) and a key reward-processing area (ventral striatum, VS) in response to high vs. low energy-dense (ED) food images using blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in obese persons in fasted and fed states. When fed, in response to high vs. low-ED food cues, obese men (vs. women) had greater functional connectivity with AMG in right subgenual anterior cingulate, whereas obese women had greater functional connectivity with AMG in left angular gyrus and right primary motor areas. In addition, when fed, AMG functional connectivity with pre/post-central gyrus was more associated with BMI in women (vs. men). When fasted, obese men (vs. women) had greater functional connectivity with AMG in bilateral supplementary frontal and primary motor areas, left precuneus, and right cuneus, whereas obese women had greater functional connectivity with AMG in left inferior frontal gyrus, right thalamus, and dorsomedial prefrontal cortex. When fed, greater functional connectivity with VS was observed in men in bilateral supplementary and primary motor areas, left postcentral gyrus, and left precuneus. These sex-based differences in functional connectivity in response to visual food cues may help partly explain differential eating behavior, pathology prevalence, and outcomes in men and women.

Assessing food acceptance in scholar children; qualitative visual record versus food waste analysis

School canteens have rules of management and supervision of menus, however has not been assessed if they are totally consumed. To assess the acceptance of food by weigh food leftovers and validation of a methodology for visual estimation in school canteens of Murcia. Participated pupils in the second and third cycle of primary education, between 8 and 12 years. The estimate of leftovers was performed by 765 food trays. Visual estimation of 300 trays was based on a categorical scale as follow: 1 (0-25%), 2 (26-50%), 3 (51- 75%), 4 (76-100%) by two dietitians and reliability was assessed with respect to the weighed food. The reliability between both methods was assessed in two samples stratified by presence or absence of school kitchen. The first dishes with leftovers were pasta, rice and vegetable purees and was higher in those schools without kitchen (p < 0.05). Also, the second dishes poultry and fish salads and vegetables garnish. Fruit and the total sum of leftovers was higher in schools without dining menus (p < 0.05). The agreement between evaluators was high in meat dishes and salads, and substantial in vegetables, pre-cooked, omelet, pasta, fish and rice. The leftlovers are high and there are differences in the acceptance of certain foods according to the type of menu offered. The visual scale is a reliable to measure acceptance indirectly, but training to catering staff is needed.

Suppressive responses by visual food cues in postprandial activities of insular cortex as revealed by magnetoencephalography

‘Hara-Hachibu’ in Japanese means a subjective sense by which we stop eating just before the motivation to eat is completely lost, a similar concept to caloric restriction (CR). Insular cortex is a critical platform which integrates sensory information into decision-making processes in eating behavior. We compared the responses of insular cortex, as assessed by magnetoencephalography (MEG), immediately after presentation of food images in the Fasting condition with those in the ‘Hara-Hachibu’ condition. Eleven healthy, right-handed males [age, 27.2±9.6 years; body mass index, 22.6±2.1kg/m2 (mean±SD)] were enrolled in a randomized, two-crossover experiment (Fasting and ‘Hara-Hachibu’ conditions). Before the MEG recordings in the ‘Hara-Hachibu’ condition, the participants consumed rice balls as much as they judged themselves to have consumed shortly before reaching satiety. During the MEG recordings, they viewed food pictures projected on a screen. The intensities of MEG responses to viewing food pictures were significantly lower in the ‘Hara-Hachibu’ condition than those in the Fasting condition (P<0.05). The intensities of the MEG responses to the visual food stimuli in the ‘Hara-Hachibu’ condition was positively associated with the factor-3 (food tasted) (r=0.693, P=0.018) and aggregated scores (r=0.659, P=0.027) of the Power of Food Scale, a self-report measure of hedonic hunger. These findings may help to elucidate the neural basis of variability of appetite phenotypes under the condition of CR among individuals, and to develop possible strategies for the maintenance of adequate CR in daily life.

Effects of Insulin Detemir and NPH Insulin on Body Weight and Appetite-Regulating Brain Regions in Human Type 1 Diabetes: A Randomized Controlled Trial

Studies in rodents have demonstrated that insulin in the central nervous system induces satiety. In humans, these effects are less well established. Insulin detemir is a basal insulin analog that causes less weight gain than other basal insulin formulations, including the current standard intermediate-long acting Neutral Protamine Hagedorn (NPH) insulin. Due to its structural modifications, which render the molecule more lipophilic, it was proposed that insulin detemir enters the brain more readily than other insulins. The aim of this study was to investigate whether insulin detemir treatment differentially modifies brain activation in response to food stimuli as compared to NPH insulin. In addition, cerebral spinal fluid (CSF) insulin levels were measured after both treatments. Brain responses to viewing food and non-food pictures were measured using functional Magnetic Resonance Imaging in 32 type 1 diabetic patients, after each of two 12-week treatment periods with insulin detemir and NPH insulin, respectively, both combined with prandial insulin aspart. CSF insulin levels were determined in a subgroup. Insulin detemir decreased body weight by 0.8 kg and NPH insulin increased weight by 0.5 kg (p = 0.02 for difference), while both treatments resulted in similar glycemic control. After treatment with insulin detemir, as compared to NPH insulin, brain activation was significantly lower in bilateral insula in response to visual food stimuli, compared to NPH (p = 0.02 for right and p = 0.05 for left insula). Also, CSF insulin levels were higher compared to those with NPH insulin treatment (p = 0.003). Our findings support the hypothesis that in type 1 diabetic patients, the weight sparing effect of insulin detemir may be mediated by its enhanced action on the central nervous system, resulting in blunted activation in bilateral insula, an appetite-regulating brain region, in response to food stimuli.Trial RegistrationClinicalTrials.gov NCT00626080.

Embryonic alcohol exposure impairs associative learning performance in adult zebrafish

The zebrafish has been proposed for modeling fetal alcohol spectrum disorders (FASD). Previous FASD research with zebrafish employed high concentrations of alcohol and/or long exposure periods. Here, we exposed zebrafish eggs to low doses of alcohol (0, 0.25, 0.50, 0.75 and 1.0% (vol/vol); external bath application of which 1/20th may reach the inside of the egg) at 16-h post-fertilization (hpf) and only for a short duration (2h) in the hope to avoid gross morphological aberrations and to mimic the more frequent FASD exposure levels. Upon reaching adulthood the exposed and control zebrafish were tested for their associative learning performance in a plus-maze. Embryonic alcohol exposure led to no gross anatomical abnormalities and did not increase mortality. Unexposed (control) zebrafish showed excellent acquisition of association between a conditioned visual stimulus (CS) and food reward, demonstrated by their preference for the target zone of the maze that contained the CS during a probe trial in the absence of reward. However, alcohol-exposed fish showed no such preference and performed indistinguishable from random chance. Locomotor activity during training and the probe trial or the amount of food consumed during training did not differ between the embryonic alcohol exposed and unexposed (control) fish, suggesting that the impaired learning performance found was unlikely to be caused by altered motivation or motor function. Our results suggest that even very small amounts of alcohol reaching the embryo for only a short duration of time may have long lasting deleterious effects on cognitive function in vertebrates.

Glucose-induced inhibition of the appetitive brain response to visual food cues in polycystic ovary syndrome patients

We postulate that insulin regulation of food intake is compromised when insulin resistance is present. In order to investigate the effect of insulin sensitivity on appetitive brain responses, we conducted functional magnetic resonance imaging studies in a group of women diagnosed with polycystic ovary syndrome (PCOS) in which insulin sensitivity ranged from normal to resistant. Subjects (n=19) were imaged while viewing pictures of high calorie (HC) foods and low calorie (LC) foods after ingesting either 75g glucose or an equivalent volume of water. The insulin sensitive group showed reduced blood oxygen level dependent (BOLD) signal in response to food pictures following glucose ingestion in numerous corticolimbic brain regions, whereas the insulin resistant group did not. There was a significant interaction between insulin sensitivity (sensitive vs resistant) and condition (water vs glucose). The largest clusters identified included the left insula, bilateral limbic/parahippocampal gyrus/culmen/midbrain, bilateral limbic lobe/precuneus, and left superior/mid temporal gyrus/parietal for HC and LC stimuli combined, the left parahippocampal gyrus/fusiform/pulvinar/midbrain for HC pictures, and the left superior/mid temporal gyrus/parietal and middle/inferior frontal gyrus/orbitofrontal cortex for LC pictures. Furthermore, BOLD signal in the anterior cingulate, medial frontal gyrus, posterior cingulate/precuneus, and parietal cortex during a glucose challenge correlated negatively with insulin sensitivity. We conclude the PCOS women with insulin resistance have an impaired brain response to a glucose challenge. The inability of postprandial hyperinsulinemia to inhibit brain responsiveness to food cues in insulin resistant subjects may lead to greater non-homeostatic eating.

The effects of high-intensity exercise on neural responses to images of food

Acute bouts of high-intensity exercise modulate peripheral appetite regulating hormones to transiently suppress hunger. However, the effects of physical activity on central appetite regulation have yet to be fully investigated. We used functional magnetic resonance imaging (fMRI) to compare neural responses to visual food stimuli after intense exercise and rest. Fifteen lean healthy men [mean ± SD age: 22.5 ± 3.1 y; mean ± SD body mass index (in kg/m(2)): 24.2 ± 2.4] completed two 60-min trials-exercise (EX; running at ∼70% maximum aerobic capacity) and a resting control trial (REST)-in a counterbalanced order. After each trial, an fMRI assessment was completed in which images of high- and low-calorie foods were viewed. EX significantly suppressed subjective appetite responses while increasing thirst and core-body temperature. Furthermore, EX significantly suppressed ghrelin concentrations and significantly enhanced peptide YY release. Neural responses to images of high-calorie foods significantly increased dorsolateral prefrontal cortex activation and suppressed orbitofrontal cortex (OFC) and hippocampus activation after EX compared with REST. After EX, low-calorie food images increased insula and putamen activation and reduced OFC activation compared with REST. Furthermore, left pallidum activity was significantly elevated after EX when low-calorie images were viewed and was suppressed when high-calorie images were viewed, and these responses correlated significantly with thirst. Exercise increases neural responses in reward-related regions of the brain in response to images of low-calorie foods and suppresses activation during the viewing of high-calorie foods. These central responses are associated with exercise-induced changes in peripheral signals related to appetite-regulation and hydration status. This trial was registered at www.clinicaltrials.gov as NCT01926431.

Influence of feeding state on neurofunctional differences between individuals who are obese and normal weight: A meta-analysis of neuroimaging studies

Obesity is a complex disorder associated with serious health risks. Examining differences in brain activity between normal weight and obese populations in response to food cues may help researchers and clinicians understand the underlying causes of overeating and obesity and help prevent them. Multiple neuroimaging studies have investigated weight differences in functional activity to food cues but have found varying results. We performed six meta-analyses of functional neuroimaging studies of weight differences in response to food images and isolated differences in processing between normal weight and obese participants. Within this study, 7 papers and 3 sets of unpublished data on functional activation to food images were analyzed using an Activation Likelihood Estimation meta-analytic approach. These analyses also addressed how feeding state impacts functional activity between weight groups. Feeding state affected weight related differences in neurofunctional activity triggered by visual food cues. In the premeal state, greater activation in the amygdala/hippocampus was found in obese participants compared to normal weight participants and, in the postmeal state, obese individuals had greater activation in the caudate and medial prefrontal cortex (MPFC) as compared to normal weight individuals. Regions of the brain associated with caloric evaluation, arousal, and memory were more active in the obese before eating, while less activity was found in an area linked to interoceptive processing. In the postmeal state, greater activity was found in the obese in areas related to risk vs. reward evaluation and reward processing. These findings may help researchers and clinicians understand and treat obesity related behaviors by identifying the altered functional regions that lead to obesity, providing a guide for future research on which neural regions need to be the target of further investigation.

Acoustic startle reactivity while processing reward‐related food cues during food deprivation: Evidence from women in different menstrual cycle phases and men

Previous research has shown that food deprivation enhances the acoustic startle reflex when it is elicited during presentation of visual food cues. Frustrative nonreward may explain this effect, since visual food cues are also rated to be more appetitive and arousing during food deprivation. However, the impact of menstrual cycle and sex on this effect remains unclear, and it is also not known whether this effect is influenced by hunger and motivation to eat. According to a within-study design, 20 healthy women in different menstrual cycle phases and 14 healthy men participated twice, in normal and food-deprived conditions. After 18 h of food deprivation, acoustic startle was attenuated by appetitive nonfood foreground pictures, but enhanced by presentation of food pictures. No differences between menstrual cycle phases and sexes appeared. The effect correlated with hunger changes, suggesting that motivational factors play a role.

Ageing diminishes the modulation of human brain responses to visual food cues by meal ingestion.

Rates of obesity are greatest in middle age. Obesity is associated with altered activity of brain networks sensing food-related stimuli and internal signals of energy balance, which modulate eating behaviour. The impact of healthy mid-life ageing on these processes has not been characterised. We therefore aimed to investigate changes in brain responses to food cues, and the modulatory effect of meal ingestion on such evoked neural activity, from young adulthood to middle age. Twenty-four healthy, right-handed subjects, aged 19.5-52.6 years, were studied on separate days after an overnight fast, randomly receiving 50 ml water or 554 kcal mixed meal before functional brain magnetic resonance imaging while viewing visual food cues. Across the group, meal ingestion reduced food cue-evoked activity of amygdala, putamen, insula and thalamus, and increased activity in precuneus and bilateral parietal cortex. Corrected for body mass index, ageing was associated with decreasing food cue-evoked activation of right dorsolateral prefrontal cortex (DLPFC) and precuneus, and increasing activation of left ventrolateral prefrontal cortex (VLPFC), bilateral temporal lobe and posterior cingulate in the fasted state. Ageing was also positively associated with the difference in food cue-evoked activation between fed and fasted states in the right DLPFC, bilateral amygdala and striatum, and negatively associated with that of the left orbitofrontal cortex and VLPFC, superior frontal gyrus, left middle and temporal gyri, posterior cingulate and precuneus. There was an overall tendency towards decreasing modulatory effects of prior meal ingestion on food cue-evoked regional brain activity with increasing age. Healthy ageing to middle age is associated with diminishing sensitivity to meal ingestion of visual food cue-evoked activity in brain regions that represent the salience of food and direct food-associated behaviour. Reduced satiety sensing may have a role in the greater risk of obesity in middle age.

Variation in the obesity risk gene FTO determines the postprandial cerebral processing of food stimuli in the prefrontal cortex

Variation in FTO is the strongest genetic determinant of body weight and has recently been linked with impaired neural processing of food stimuli. However, whether this brain-expressed gene affects neuronal processing of food-related stimuli after ingestion is still poorly understood. In this study, twenty-four participants were examined before, 30 and 120min after ingesting 75g of glucose solution or water on two separate days. Functional magnetic resonance imaging (fMRI) during visual food presentation was performed. All participants were genotyped for FTO SNP rs8050136. We detected significant differences between FTO genotypes in the prefrontal cortex 30min post-glucose load in BOLD-response to food pictures (p=0.0017), while no differences were detected in response to water ingestion or 120min post-glucose load. Since the prefrontal cortex plays a major role in the inhibitory control of eating, we propose that reduced postprandial activity in FTO risk allele carriers contributes to overeating and obesity.

Effect of protein status on brain reward responses to food cues

Protein is an indispensable component within the human diet. Following a protein deficit, food preferences change to restore adequate protein status. We investigated the concomitant changes in brain responses to food cues associated with protein. A randomized cross-over design was used, consisting of two 16-day fully controlled dietary interventions involving consumption of individualized, isoenergetic menus providing either 0.6 g protein/kg BW/day (low-protein diet ∼7 en% derived from protein), or 2.2 g protein/kg BW/day (high-protein diet ∼25 en%). The interventions were followed by a 1-day ad libitum -phase, where energy and protein intake were measured. Brain responses to odour and visual food cues varying in taste (sweet/savoury) and protein content (high/low) were measured using functional magnetic resonance imaging (fMRI). Twenty-four healthy, unrestrained females participated (age: 22 ± 2 y; BMI: 22.4 ± 1.8 kg/m 2 ). Protein intake was 8% higher after the low-compared with the high-protein diet (95 g vs. 103 g, p < 0.05), whereas total energy intake did not differ. When exposed to odour and visual food cues, brain activation in reward-related areas (orbitofrontal cortex, striatum, insula) was higher after the low- compared with the high-protein diet. Specifically, when exposed to savoury food cues, brain activation was higher in the OFC. The protein content of food cues did not affect brain activation differently. In conclusion, human protein intake appears to be controlled in a very specific manner involving food selection guided by taste quality rather than by protein content. We are the first to provide neural evidence for changes in food preference driven by macronutrient depletion.

Resting-state synchrony between anterior cingulate cortex and precuneus relates to body shape concern in anorexia nervosa and bulimia nervosa

Cortical areas supporting cognitive control and salience demonstrate different neural responses to visual food cues in patients with eating disorders. This top-down cognitive control, which interacts with bottom-up appetitive responses, is tightly integrated not only in task conditions but also in the resting-state. The dorsal anterior cingulate cortex (dACC) is a key node of a large-scale network that is involved in self-referential processing and cognitive control. We investigated resting-state functional connectivity of the dACC and hypothesized that altered connectivity would be demonstrated in cortical midline structures involved in self-referential processing and cognitive control. Seed-based resting-state functional connectivity was analyzed in women with anorexia nervosa (N=18), women with bulimia nervosa (N=20) and age matched healthy controls (N=20). Between group comparisons revealed that the anorexia nervosa group exhibited stronger synchronous activity between the dACC and retrosplenial cortex, whereas the bulimia nervosa group showed stronger synchronous activity between the dACC and medial orbitofrontal cortex. Both groups demonstrated stronger synchronous activity between the dACC and precuneus, which correlated with higher scores of the Body Shape Questionnaire. The dACC-precuneus resting-state synchrony might be associated with the disorder-specific rumination on eating, weight and body shape in patients with eating disorders.