Insomnia symptoms are highly prevalent and associated with several adverse medical conditions, but only few determinants, including non-modifiable ones, have been highlighted. We investigated associations between body silhouette trajectories over the lifespan and insomnia symptoms in adulthood. From a community-based study, 7 496 men and women aged 50-75 years recalled their body silhouette at age 8, 15, 25, 35 and 45, and rated the frequency of insomnia symptoms on a standardized sleep questionnaire. An Epworth Sleepiness Scale ≥11 defined excessive daytime sleepiness (EDS). Using a group-based trajectory modeling, we identified five body silhouette trajectories: a 'lean-stable' (32.7%), a 'heavy-stable' (8.1%), a 'moderate-stable' (32.5%), a 'lean-increase' (11%) and a 'lean-marked increase' (15.7%) trajectory. In multivariate logistic regression, compared to the 'lean-stable' trajectory, the 'lean-marked increase' and 'heavy-stable' trajectories were associated with a significant increased odd of having ≥1 insomnia symptoms as compared to none and of having a proxy for insomnia disorder (≥1 insomnia symptom and EDS). The association with the 'lean-marked increase' trajectory' was independent from body mass index measured at study recruitment. In conclusion, increasing body silhouette over the lifespan is associated with insomnia symptoms in adulthood, emphasizing the importance of weight gain prevention during the entire lifespan.