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

•Between-network connectivity (BNC) assessed exercise effects on brain connectivity.•BNC in the posterior cingulate cortex was reduced following chronic exercise.•Change in BNC was related to changes in aerobic fitness level and perceived hunger.•Exercise effects on BNC may contribute to individual responsivity to exercise.

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.