Introduction: The prevalence of obesity within countries varies by gender, age, socioeconomic status, and culture. These determinants appear to predict obesity differently in different countries. The objective of this study was to estimate the impact of these determinants on obesity in a representative sample of the Lebanese adult population. Methods: A cross-sectional survey of 2697 adults aged ≥ 20 years, excluding pregnant and lactating women, was conducted in 2008. Households were selected randomly from all Governates of Lebanon based on a stratified cluster sampling. One randomly-sampled adult was interviewed in each visited household; demographic, socioeconomic and anthropometric data were measured. Dietary intake was obtained using a 24-hour recall instrument. The prevalence of obesity in 2008 was estimated. Logistic regressions analysis was carried out to assess the relationship between energy intake and obesity as well as adjusted relevant variables, excluding data from participants who reported implausible energy intakes. Results: Currently, approximately one in four Lebanese adults is obese. While men and women showed overall similar prevalence rates of obesity, gender disparities were noted across obesity classes and age groups. In males, the odds of being obese increased among those married, employed, and owning increased household assets; the opposite was the case for women. Obesity in women decreased with increasing household wealth. In women also, there was a positive association between obesity and energy intake, and a negative association between obesity and physical activity. Obese adults reported consuming a higher percentage of their energy intake from fat, and a lower intake from cereals, compared with their non-obese counterparts. Conclusion: The prevalence of obesity among Lebanese adults is on the rise, with significant demographic and socioeconomic differentials. High energy consumption and inactivity of Lebanese adults, as well as several complex socioeconomic and cultural elements, are contributing factors to the estimated high rates of obesity.