Changes in olive oil consumption and long-term body weight changes in 3 United States prospective cohort studies.

Background: Olive oil intake is inversely associated with 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 Professionals Follow-up Study (1990-2014), aged 65 y or younger and who were free from chronic disease at baseline. We assessed the associations between changes in olive oil intake within each 4-y interval and concurrent body weight changes using multivariable linear regression models. Results across the 3 cohorts were pooled using inverse-variance weights.

Results: At baseline, the mean body mass index (BMI in kg/m) was between 25.9 and 26.1 across the 3 cohorts. The mean weight change over each of the 4-y follow-up cycles was highest in the NHSII (1.8 kg; 95% CI [confidence interval]: -6.8, 11.3 kg), followed by the NHS (1.2 kg; 95% CI: -6.8, 9.1 kg), and lastly the health professionals follow-up study (0.9 kg; 95% CI: 5.4, 7.3 kg). After multivariable adjustment, each ½ tablespoon (7 g) serving per day increment in olive oil consumption was inversely associated with body weight (β coefficient: -0.09 kg, 95% CI: -0.11, -0.08 kg; P < 0.0001). In contrast, each 7 g serving per day increase in other types of added fat (vegetable oils, butter, and margarine) was positively associated with changes in body weight. Results were consistent in stratified analyses by age and BMI. In substitution analyses, replacing margarine, butter, and other vegetable oils with equal amounts of olive oil was associated with less weight gain.

Conclusions: A long-term increase in olive oil intake was inversely associated with body weight in middle-aged adults in the United States. Conversely, increased consumption of other added fats, such as butter and margarine, was positively associated with body weight.