Disadvantaged socioeconomic status is arguably the one exposure that has most consistently been linked to obesity, even more strongly so than diet and physical inactivity, which are the two main perceived root causes of weight gain. However, we still know very little about the relationship between having a disadvantaged social position and excessive fat accumulation, particularly when it comes to whether the relationship in question can also be seen as a long-term one, i.e., spanning from childhood to adulthood. By making use of the unique Stockholm Birth Cohort Multigenerational Study, the present study uses generalized ordered logistic regressions to examine the association between sociometrically assessed peer status position in school at age 13 and excessive fat accumulation at age 32. The results suggest that the odds of having excessive fat accumulation are about 0.5 times lower among popular and accepted children (ORs = 0.52 and 0.56, respectively), compared to those with a marginalized peer status position, independent of other obesogenic risk factors measured both prior and subsequent to peer status position. Our results give support to the notion that improved weight status may be another positive consequence of policies aiming to increase social inclusion within schools.