Sonja Yokum

Body mass correlates inversely with inhibitory control in response to food among adolescent girls: an fMRI study

Self-report and behavioral data suggest that impulsivity may contribute to the development and maintenance of obesity. Neuroimaging studies implicate a widespread neural network in inhibitory control and suggest that impulsive individuals show hypoactivity in these regions during tasks requiring response inhibition. Yet, research has not directly tested whether body mass correlates inversely with activation of these regions during response inhibition tasks. The present study used functional magnetic resonance imaging (fMRI) to investigate neural activations during a food-specific go/no-go task in adolescent girls ranging from lean to obese. When required to inhibit prepotent responses to appetizing food, body mass index (BMI) correlated with response inhibition at both the behavioral and neural levels, with more overweight adolescents showing greater behavioral evidence of impulsivity as well as reduced activation of frontal inhibitory regions, including superior frontal gyrus, middle frontal gyrus, ventrolateral prefrontal cortex, medial prefrontal cortex, and orbitofrontal cortex, than leaner individuals. As well, activation in food reward regions (e.g., temporal operculum/insula) in response to food images correlated positively with BMI. Results suggest that hypofunctioning of inhibitory control regions and increased response of food reward regions are related to elevated weight.

Weight Gain Is Associated with Reduced Striatal Response to Palatable Food

Consistent with the theory that individuals with hypofunctioning reward circuitry overeat to compensate for a reward deficit, obese versus lean humans have fewer striatal D2 receptors and show less striatal response to palatable food intake. Low striatal response to food intake predicts future weight gain in those at genetic risk for reduced signaling of dopamine-based reward circuitry. Yet animal studies indicate that intake of palatable food results in downregulation of D2 receptors, reduced D2 sensitivity, and decreased reward sensitivity, implying that overeating may contribute to reduced striatal responsivity. Thus, we tested whether overeating leads to reduced striatal responsivity to palatable food intake in humans using repeated-measures functional magnetic resonance imaging. Results indicated that women who gained weight over a 6 month period showed a reduction in striatal response to palatable food consumption relative to weight-stable women. Collectively, results suggest that low sensitivity of reward circuitry increases risk for overeating and that this overeating may further attenuate responsivity of reward circuitry in a feedforward process.

Reward circuitry responsivity to food predicts future increases in body mass: moderating effects of DRD2 and DRD4.

OBJECTIVE To determine whether responsivity of reward circuitry to food predicts future increases in body mass and whether polymorphisms in DRD2 and DRD4 moderate these relations. DESIGN The functional magnetic resonance imaging (fMRI) paradigm investigated blood oxygen level dependent activation in response to imagined intake of palatable foods, unpalatable foods, and glasses of water shown in pictures. DNA was extracted from saliva samples using standard salting-out and solvent precipitation methods. PARTICIPANTS Forty-four adolescent female high school students ranging from lean to obese. MAIN OUTCOME Future increases in body mass index (BMI). RESULTS Weaker activation of the frontal operculum, lateral orbitofrontal cortex, and striatum in response to imagined intake of palatable foods, versus imagined intake of unpalatable foods or water, predicted future increases in body mass for those with the DRD2 TaqIA A1 allele or the DRD4-7R allele. Data also suggest that for those lacking these alleles, greater responsivity of these food reward regions predicted future increases in body mass. DISCUSSION This novel prospective fMRI study indicates that responsivity of reward circuitry to food increases risk for future weight gain, but that genes that impact dopamine signaling capacity moderate the predictive effects, suggesting two qualitatively distinct pathways to unhealthy weight gain based on genetic risk.

Attentional Bias to Food Images Associated With Elevated Weight and Future Weight Gain: An fMRI Study

Behavioral studies reveal that obese vs. lean individuals show attentional bias to food stimuli. Yet research has not investigated this relation using objective brain imaging or tested whether attentional bias to food stimuli predicts future weight gain, which are important aims given the prominence of food cues in the environment. We used functional magnetic resonance imaging (fMRI) to examine attentional bias in 35 adolescent girls ranging from lean to obese using an attention network task involving food and neutral stimuli. BMI correlated positively with speed of behavioral response to both appetizing food stimuli and unappetizing food stimuli, but not to neutral stimuli. BMI correlated positively with activation in brain regions related to attention and food reward, including the anterior insula/frontal operculum, lateral orbitofrontal cortex (OFC), ventrolateral prefrontal cortex (vlPFC), and superior parietal lobe, during initial orientation to food cues. BMI also correlated with greater activation in the anterior insula/frontal operculum during reallocation of attention to appetizing food images and with weaker activation in the medial OFC and ventral pallidum during reallocation of attention to unappetizing food images. Greater lateral OFC activation during initial orientation to appetizing food cues predicted future increases in BMI. Results indicate that overweight is related to greater attentional bias to food cues and that youth who show elevated reward circuitry responsivity during food cue exposure are at increased risk for weight gain.

Youth at Risk for Obesity Show Greater Activation of Striatal and Somatosensory Regions to Food

Obese humans, compared with normal-weight humans, have less striatal D2 receptors and striatal response to food intake; weaker striatal response to food predicts weight gain for individuals at genetic risk for reduced dopamine (DA) signaling, consistent with the reward-deficit theory of obesity. Yet these may not be initial vulnerability factors, as overeating reduces D2 receptor density, D2 sensitivity, reward sensitivity, and striatal response to food. Obese humans also show greater striatal, amygdalar, orbitofrontal cortex, and somatosensory region response to food images than normal-weight humans do, which predicts weight gain for those not at genetic risk for compromised dopamine signaling, consonant with the reward-surfeit theory of obesity. However, after pairings of palatable food intake and predictive cues, DA signaling increases in response to the cues, implying that eating palatable food contributes to increased responsivity. Using fMRI, we tested whether normal-weight adolescents at high- versus low-risk for obesity showed aberrant activation of reward circuitry in response to receipt and anticipated receipt of palatable food and monetary reward. High-risk youth showed greater activation in the caudate, parietal operculum, and frontal operculum in response to food intake and in the caudate, putamen, insula, thalamus, and orbitofrontal cortex in response to monetary reward. No differences emerged in response to anticipated food or monetary reward. Data indicate that youth at risk for obesity show elevated reward circuitry responsivity in general, coupled with elevated somatosensory region responsivity to food, which may lead to overeating that produces blunted dopamine signaling and elevated responsivity to food cues.

Relation of regional gray and white matter volumes to current BMI and future increases in BMI: a prospective MRI study.

Objective:This study tested whether global and regional brain volumes correlated with body mass index (BMI) and increases in BMI over 1-year follow-up.Methods:A total of 83 young females (M age=18.4, s.d.=2.8; BMI range=17.3–38.9) were scanned using magnetic resonance imaging. Voxel-based morphometry was used to assess global brain volume and regional gray matter (GM) and white matter (WM) volumes in regions implicated in taste, reward and inhibitory control.Results:Obese participants had less total GM volume than lean and overweight participants. Obese participants had lower total WM volume than overweight participants. BMI correlated with higher WM volumes in the middle temporal gyrus, fusiform gyrus, parahippocampal gyrus, Rolandic operculum and dorsal striatum. Trend-level reduced GM volumes in the superior frontal gyrus and middle frontal gyrus were related to increases in BMI over 1-year follow-up.Conclusion:Findings suggest that BMI is related to global and regional differences in brain matter volume in female adolescents. Most importantly, findings suggest that low GM volume in regions implicated in inhibitory control are related to future weight gain. Results taken in conjunction with prior findings suggest that abnormalities in regional GM volumes, but not WM volumes, increase the risk for future weight gain and abnormalities in regional WM volumes, but not GM volumes, are secondary to weight gain.

Eating Disorder Prevention: Current Evidence-Base and Future Directions

OBJECTIVE This narrative review sought to (a) characterize prevention programs that have produced reliable, reproducible, and clinically meaningful effects in efficacy trials, (b) discuss effectiveness trials that have tested whether prevention programs produce intervention effects under ecologically valid real-world conditions, (c) discuss dissemination efforts and research on dissemination, and (d) offer suggestions regarding directions for future research in this field. CONCLUSION A literature revealed that 6 prevention programs have produced significant reductions in eating disorder symptoms through at least 6-month follow-up and that 2 have significantly reduced future eating disorder onset. Effectiveness trials indicate that 2 prevention programs have produced effects under ecologically valid conditions that are only slightly attenuated. Although there have been few dissemination efforts, evidence suggests that a community participatory approach is most effective. Lastly, it would be useful to develop programs that produce larger and more persistent reductions in eating disorder symptoms and eating disorder onset, focus more on effectiveness trials that confirm that prevention programs produce clinically meaningful effects under real-world conditions, conduct meditational, mechanisms of action, and moderator research that provides stronger support for the intervention theory of prevention programs, and investigate the optimal methods of disseminating and implementing evidence-based prevention programs.

An fMRI study of obesity, food reward, and perceived caloric density. Does a low-fat label make food less appealing? ☆

We tested the hypothesis that obese individuals experience greater activation of the gustatory and somatosensory cortex, but weaker activation of the striatum, in response to intake and anticipated intake of high-fat chocolate milkshake versus an isocaloric milkshake labeled low-fat and a tasteless solution using functional magnetic resonance imaging (fMRI) with 17 obese and 17 lean young women. Obese relative to lean women showed greater activation in somatosensory (Rolandic operculum), gustatory (frontal operculum), and reward valuation regions (amgydala, ventralmedial prefrontal cortex (vmPFC) in response to intake and anticipated intake of milkshake versus tasteless solution, though there was little evidence of reduced striatal activation. Obese relative to lean women also showed greater activation in the Rolandic operculum, frontal operculum, and vmPFC in response to isocaloric milkshakes labeled regular versus low-fat. Results suggest that hyper-responsivity of somatosensory, gustatory, and reward valuation regions may be related to overeating and that top-down processing influence reward encoding, which could further contribute to weight gain.

Multilocus Genetic Composite Reflecting Dopamine Signaling Capacity Predicts Reward Circuitry Responsivity

The objective of the study was to test the hypotheses that humans with genotypes putatively associated with low dopamine (DA) signaling capacity, including the TaqIA A1 allele, DRD2-141C Ins/Ins genotype, DRD4 7-repeat or longer allele, DAT1 10-repeat allele, and the Met/Met COMT genotype, and with a greater number of these genotypes per a multilocus composite, show less responsivity of reward regions that primarily rely on DA signaling. Functional magnetic resonance imaging (fMRI) paradigms were used to investigate activation in response to receipt and anticipated receipt of palatable food and monetary reward. DNA was extracted from saliva using standard methods. Participants were 160 adolescents (mean age = 15.3 years, SD = 1.07 years; mean body mass index = 20.8, SD = 1.9). The main outcome was blood oxygenation level-dependent activation in the fMRI paradigms. Data confirmed that these fMRI paradigms activated reward, attention, somatosensory, and gustatory regions. Individuals with, versus without, these five genotypes did not show less activation of DA-based reward regions, but those with the Met/Met versus the Val/Val COMT genotype showed less middle temporal gyrus activation and those with the DRD4-L versus the DRD4-S genotype showed less middle occipital gyrus activation in response to monetary reward. Critically, the multilocus composite score revealed that those with a greater number of these genotypes showed less activation in reward regions, including the putamen, caudate, and insula, in response to monetary reward. The results suggest that the multilocus genetic composite is a more sensitive index of vulnerability for low reward region responsivity than individual genotypes.

Cognitive regulation of food craving: Effects of three cognitive reappraisal strategies on neural response to palatable foods

Objective:Obese versus lean individuals show greater reward region and reduced inhibitory region responsivity to food images, which predict future weight gain. Thinking of the costs of eating palatable foods and craving suppression have been found to modulate this neural responsivity, but these cognitive reappraisal studies have primarily involved lean participants. Herein we evaluated the efficacy of a broader range of reappraisal strategies in modulating neural responsivity to palatable food images among individuals who ranged from lean to obese and tested whether body mass index (BMI) moderates the effects of these strategies.Materials and methods:Functional magnetic resonance imaging assessed the effects of three cognitive reappraisal strategies in response to palatable food images versus an imagined intake comparison condition in a sample of adolescents (N=21; M age=15.2).Results:Thinking of the long-term costs of eating the food, thinking of the long-term benefits of not eating the food and attempting to suppress cravings for the food increased activation in inhibitory regions (for example, superior frontal gyrus, ventrolateral prefrontal cortex) and reduced activation in attention-related regions (for example, precuneus and posterior cingulate cortex). The reappraisal strategy focusing on the long-term benefits of not eating the food more effectively increased inhibitory region activity and reduced attention region activity compared with the other two cognitive reappraisal strategies. BMI did not moderate the effects.Discussion:These novel results imply that cognitive reappraisal strategies, in particular those focusing on the benefits of not eating the food, could potentially increase the ability to inhibit appetitive motivation and reduce unhealthy food intake in overweight individuals.