<i>Background:</i> Olive oil is an energy-dense food frequently consumed in south European countries with increasingly high obesity prevalence. Evidence of the impact of olive oil consumption on BMI and the risk of obesity is limited. We analyzed this association taking into consideration the problem of energy underreporting. <i>Methods: </i>Cross-sectional data on 6,352 Spanish adults were analyzed. Dietary intake was assessed using a validated food frequency questionnaire. Height and weight were measured. <i>Results: </i>Higher olive oil consumption was not associated with energy compensation in the overall diet. Olive oil consumptionwas positively associated (p < 0.004) with BMI in non-energy-adjusted multivariate linear regression models. Statistical significance of this association disappeared after controlling for energy intake in plausible energy intake reporters. The obesity risk increased for olive oil consumption of more than 2 tablespoons/day in both plausible energy intake reporters (odds ratio 1.30 (95% CI 1.01–1.70)) and energy intake underreporters (odds ratio 3.06 (95% CI 2.15–4.35)). This association was not significant after additional adjustment for energy intake (odds ratio 1.19 (95% CI 0.91–1.56)) in plausible energy intake reporters. <i>Conclusion: </i>Olive oilintake did not affect BMI and the risk of obesity after adjustment for total energy intake in plausible energy intake reporters. The lack of energy intake compensation for olive oil consumption might explain the positive associations in models not adjusted for energy.