Altered Default Network Activity in Obesity

Abstract

The regulation of energy intake is a complex process involving the integration of homeostatic signals and both internal and external sensory inputs. To better understand the neurobiology of this process and how it may be dysfunctional in obesity, this study examined activity of the brain’s “default network” in reduced-obese (RO) as compared to lean individuals. The default network is a group of functionally connected brain regions thought to play an important role in internally directed cognitive activity and the interplay between external and internal sensory processing. Functional magnetic resonance imaging was performed in 24 lean and 18 RO individuals in the fasted state after 2 days of eucaloric energy intake and after 2 days of 30% overfeeding in a counterbalanced design. Scanning was performed while subjects passively viewed images of food and nonfood objects. Independent component analysis was used to identify the default network component. In the eucaloric state, greater default network activity was observed in RO compared to lean individuals in the lateral inferior parietal and posterior cingulate cortices. Activity was positively correlated with appetite. Overfeeding resulted in increased default network activity in lean but not RO individuals. These findings suggest that the function of the default network, a major contributor to intrinsic neuronal activity, is altered in obesity and/or obese-prone individuals. Future studies of the network’s function and its relationship to other brain networks may improve our understanding of the mechanisms and treatment of obesity.

Reduced salience and default mode network activity in women with anorexia nervosa

“…Relevant to foodrelated behaviours, previous studies have found increased SN and DMN activity in obese individuals, both at rest and across task performance. [35][36][37] A small number of previous studies have investigated functional connectivity in people with anorexia nervosa, although, to our knowledge, ours is the first study to investigate the DMN and SN in currently ill women and to compare activity in these networks between ill and recovered women. Favaro and colleagues 38 found decreased activity in the ventral visual network in people with anorexia nervosa and those recovered from the disease compared with controls, but they also found increased activity in the somatosensory network in those with anorexia nervosa.…”

“…As previous studies have found increased intrinsic DMN activity in obese individuals, we hypothesized that DMN activity in women with anorexia nervosa would be reduced and thus opposite to that seen in obesity. 35,37 Based on the findings of Cowdrey and colleagues, who showed increased DMN activity in individuals recovered from anorexia nervosa, we hypothesized that altered DMN activity is dependent on illness state and that reduced activity would be observed only in women with anorexia nervosa compared with controls. To our knowledge, no previous studies have investigated SN activity in women with anorexia nervosa or recovered women, but based on previous findings of increased SN activity in an obese sample, 36 we hypothesized that we would observe reduced SN activity in women with anorexia nervosa.…”

The association between ADHD and eating disorders/pathology in adolescents: A systematic review

“…In addition, overeating itself may give rise to ADHD-related symptoms. Some limited evidence suggests such an association; for example, short-term lab-based over-feeding studies in non-obese humans have been shown to lead to brain changes including an increase in the activation of the default mode network (DMN) [32]. ADHD is characterized by DMN over-activation and difficulty in suppressing this network during effortful tasks [33,34].…”

Obesity is marked by distinct functional connectivity in brain networks involved in food reward and salience

“…The brain plays a crucial role in the decision to eat by integrating the multiple hormonal and neuronal signals [3]. Not surprisingly, there is increasing evidence that obesity is associated with changes in the central nervous system [4][5][6][7][8].…”