Prevalence of excess weight varies substantially by socioeconomic position (SEP). SEP can be defined with different indicators. The strength of the association of SEP with excess weight differs by SEP indicator, between populations and over time. We examined the prevalence of overweight and obesity (body mass index 25–29.9 and ≥30 kg m−2) in Switzerland by educational level, household income tertile and occupational class (three categories for each indicator). Self-reported data stem from four cross-sectional population surveys including 53 588 persons aged between 25 and 74 years. The overall prevalence of overweight increased between 1992 and 2007 from 37.4% to 41.4% in men and from 18.8% to 21.9% in women. Obesity prevalence increased from 7.2% to 9.7% in men and from 5.4% to 8.6% in women. Inequalities were calculated with multivariable logistic regression. Inequalities were larger in women than in men and for obesity than for overweight. However, overweight and obesity inequalities did not significantly change over time, despite overall increasing prevalence. Although all SEP indicators were independently associated with excess weight, the association was strongest with education, particularly in women. Programmes and policies aimed at preventing excess weight should target individuals with low education early in life.