<p>Extremes of Body Mass Index (BMI) spectrum have been linked to impaired executive functions, including inhibitory control. While altered neural responses are documented in overweight and obese individuals, less is known about the full BMI spectrum, particularly in underweight adults. This study examined behavioral and neural correlates of reactive inhibition across four BMI groups (underweight, normal-weight, overweight, obese) in 87 young adults (<i>M</i>age = 22.82, <i>SD</i> = 4.18). Participants performed a Go/NoGo task in neutral and food-related contexts while EEG was recorded. Analyses focused on N2d and P3d components. No behavioral differences emerged between groups. However, P3d amplitudes (but not N2d) showed significant BMI-related modulation (<i>F</i>(3,83) = 2.76, <i>p</i> = 0.047), driven by larger amplitudes in overweight participants compared to underweight and normal-weight individuals. Curve estimation analysis revealed a significant quadratic relationship between BMI and P3d amplitude (<i>R</i>^<i>2</i> = 0.073, <i>p</i> = 0.041), which provided a superior fit compared to the linear model <i>(R</i>^<i>2</i> <i>= 0.061</i>,<i> p</i> = 0.021). Elevated BMI is associated with increased neural recruitment during inhibition, suggesting a compensatory mechanism to maintain behavioral performance. The quadratic pattern suggests that this compensatory efficiency reaches a plateau or begins to stabilize beyond the overweight range. These findings highlight the importance of indexing neural inhibitory markers to identify cognitive vulnerabilities in weight regulation.</p>