“Free won't” of food in overweight and normal-weight adults: Comparison of neurocognitive correlates of intentional and reactive inhibitions

Food-related inhibition plays a critical role in the manifestation of overweight. Previous research has focused exclusively on stimulus-driven (reactive) inhibition, which is different from intentional inhibition that refers to an internally generated decision to "stop". This study investigated the food-related neurophysiological correlates of intentional and reactive inhibitions in overweight and normal-weight adults. We compared 35 overweight participants (OWs) and 34 normal-weight participants (NWs) on performance and electroencephalography-based measures during a food-related go/no-go/choose task. In this task, participants made reactive responses to an instructed go/no-go target or made intentional choices whether to execute or inhibit a keypress when presented with a free-choice target. Our results mainly showed, 1) for group-difference, N2a amplitudes of OWs were less negative than that of NWs in the intentional trials; 2) for source difference, N2a amplitudes were less negative in reactive condition than in intentional condition uniquely in OWs. Moreover, comparison across intentional responses revealed that P2 amplitudes in no-go trials were lower than in go trials. Additionally, a greater body mass index correlated with lower intentional no-go-P2 and reactive go/no-go-P2 amplitudes. These findings suggest that overweight is associated with deficits in food-related intentional inhibition, which is segregated from reactive inhibition. The individual differences in premotor inhibition during free-choice situations might provide an explanation for overeating behaviors in overweight adults' daily life. Further, our results refine the ERP marker of intentional inhibition from N2 to N2a, which could be an essential neural mechanism underlying the "free won't" of food in OWs.