Exercise-related changes in between-network connectivity in overweight/obese adults

Abstract

Understanding how exercise affects communication across the brain in overweight/obese individuals may provide insight into mechanisms of weight loss and maintenance. In the current study, we examined the effects of a 6-month exercise program in 11 overweight/obese individuals (mean BMI: 33.6±1.4 mg/kg2; mean age: 38.2±3.2 years) on integrative brain “hubs,” which are areas with high levels of connectivity to multiple large-scale networks thought to play an important role in multimodal integration among brain regions. These integrative hubs were identified with a recently developed between-network connectivity (BNC) metric, using functional magnetic resonance imaging (fMRI). BNC utilizes a multiple regression analysis approach to assess relationships between the time series of large-scale functionally-connected brain networks (identified using independent components analysis) and the time series of each individual voxel in the brain. This approach identifies brain regions with high between-network interaction, i.e., areas with high levels of connectivity to many large-scale networks. Changes in BNC following exercise were determined using paired t-tests, with results considered significant at a whole-brain level if they exceeded a voxel-wise threshold of p < 0.01 and cluster-level family-wise error (FWE) correction for multiple comparisons of p < 0.05. Following the intervention, BNC in the posterior cingulate cortex (PCC) was significantly reduced (p < 0.001). The changes driving the observed effects were explored using Granger causality, finding significant reductions in both outgoing causal flow from the PCC to a number of networks (p < 0.05; language network, visual network, sensorimotor network, left executive control network, basal ganglia network, posterior default mode network), in addition to reductions in ingoing causal flow to the PCC from a number of networks (p < 0.05; ventral default mode network, language network, sensorimotor network, basal ganglia network). Change in BNC was related to changes in aerobic fitness level (VO2 max; p = 0.008) and perceived hunger (Three Factor Eating Questionnaire; p = 0.040). Overall, the impact of exercise on communication between large-scale networks may contribute to individual responsivity to exercise.

Higher body mass index is associated with reduced posterior default mode connectivity in older adults

“…Concerning further associations of BMI and functional connectivity, only the visual network was found to be associated with higher BMI, but the extent of increased connectivity was very limited. In our large cohort, we did not observe previously reported increased putamen and insula connectivity [Hogenkamp et al, 2016], decreased insula-anterior cingulate cortex (ACC) connectivity [Moreno-Lopez et al, 2016], increased salience network connectivity [Figley et al, 2016;Garcia-Garcia et al, 2013], reduced temporal lobe network connectivity [Kullmann et al, 2012] or increased DMN connectivity [Kullmann et al, 2012;Legget et al, 2016;Tregellas et al, 2011] with higher BMI. Similar to our results, one study reported reduced precuneus connectivity for obese compared with lean participants, although the results might have been confounded by the significant age difference between groups [Geha et al, 2016].…”

The Impact of Physical Activity on Food Reward: Review and Conceptual Synthesis of Evidence from Observational, Acute, and Chronic Exercise Training Studies

“…Two studies found a reduction in implicit wanting for high-fat relative to low-fat foods after exercise training [54,62]. This may be a result of a direct effect of exercise on brain regions related to food reward, as shown by the fMRI studies included in the current review, and others [73,74]. Furthermore, as exercise affects cognition and executive function, it has been proposed that processes such as inhibitory control could have a moderating effect on wanting and modulate eating behavior [66].…”

Bariatric surgery in obese patients reduced resting connectivity of brain regions involved with self‐referential processing

“…DMN is a network most active while processing internal mental status, such as self-referential thinking/autobiographical memory, and during external unfocused attention (Andrews-Hanna, Smallwood, & Spreng, 2014). Previous studies found that PCC activity was increased in obese/overweight individuals (Kullmann et al, 2012) and that activity in this region was reduced following chronic exercise (Legget et al, 2016). PCC activation has also been observed during presentation of visual food cues and during food tasting (DelParigi, Chen, Salbe, Reiman, & Tataranni, 2005).…”