Background Social mobility (movement up or down the social hierarchy) and social accumulation (accumulating social advantage or disadvantage) across the life course have been shown to affect adult health. There is no evidence on how these processes simultaneously affect adult overweight and obesity.

Methods Cross-sectional analysis using data from phase 5 of the Whitehall II study (1997–1999), including retrospective information on past socioeconomic position (SEP) for 4598 participants (44–69 years). The effect of social mobility and social accumulation, from childhood social class to educational attainment to current employment grade, on prevalent adult overweight and obesity was examined.

Results Upwardly socially mobile participants did not have lower prevalence of overweight and obesity compared to the socially stable at low SEP (62.3 vs 63.9% in women). Downwardly socially mobile participants had higher prevalence of overweight and obesity than the socially stable at high SEP (52.0% vs 36.1% in women). The odds of adult overweight and obesity increased with social accumulation of disadvantage. Among women, one life phase in low SEP was associated with 61% higher odds (OR 1.61; 95% CI 1.05 to 2.47), two phases low with 66% higher odds (1.66; 1.14 to 2.42) and all phases low with 2.6 times the odds (2.61; 1.79 to 3.78) of overweight and obesity compared to women with all phases in high SEP.

Conclusions Social mobility and social accumulation can operate simultaneously across the life course. Prevention of downward social mobility and social accumulation of disadvantage could reduce the overall prevalence of adult overweight and obesity.