BACKGROUND: Olive oil intake is inversely associated with the risk of cardiometabolic diseases. However, its energy density has raised concerns about weight gain. In this prospective cohort study, we examined the associations between long-term changes in olive oil consumption and changes in body weight. METHODS: We examined data from 121,119 females and males from the Nurses' Health Study (NHS,1990-2010), NHSII (1991-2015), and Health Professional's Follow-up Study (HPFS,1990-2014), aged 65 years or younger and who were free from chronic disease at baseline. We assessed the associations between changes in olive oil intake within each 4-year interval and concurrent body weight changes using multivariable linear regression models. Results across the three cohorts were pooled using inverse-variance weights. RESULTS: At baseline, the mean body mass index (BMI) was between 25.9 and 26.1 kg/m CONCLUSIONS: A long-term increase in olive oil intake was inversely associated with body weight in middle-aged adults in the U.S. Conversely, increased consumption of other added fats, such as butter and margarine, was positively associated with body weight.