Various personality domains and facets correlate with body mass index (BMI), but recent studies suggest that using narrower personality traits—nuances—could contribute to a more detailed understanding of personality–body weight associations. We used three large datasets with different inventories to describe nuances’ correlations with BMI and explore whether BMI predominantly correlated with affective, behavioral, cognitive, or motivational item content. BMI correlated with many nuances, most prominently those reflecting immoderation, lack of orderliness, talkativeness, leadership tendencies, anger, traditionalism, and preference for routine. The highest nuance-level correlation was .21, compared to .11 for the Five-Factor Model domains. BMI correlated most strongly with nuances predominantly reflecting behaviors. Nuance-based approaches can thus reveal the strength, multitude, and content-nature of personality–outcome correlations that can potentially remain hidden in broader traits. If personality traits become relevant in the prevention or treatment of obesity, a focus on narrow behavioral traits may be especially warranted.