This study examined the association of obesity-related eating behaviors (OREB) with physical activity, sedentariness, and diet quality. Data were taken from a cross-sectional study in 10,791 persons representative of the Spanish population who were ≥18 y of age in 2008-2010. The following self-reported information was collected on 12 OREB: not planning how much to eat before sitting down, not deciding the amount of food on the plate, skipping breakfast, eating precooked/canned food or snacks bought at vending machines or at fast-food restaurants, not choosing low-energy foods, not removing visible fat from meat or skin from chicken, eating while watching television or seated on a sofa or an armchair, and taking a short time for meals. Analyses were performed with linear or logistic regression, as appropriate, and adjusted for the main confounders. In comparison to participants with ≤1 OREB, those with ≥5 OREB performed less physical activity [β: -2.61 (95% CI: -4.44, -0.78); P-trend < 0.001] and spent more time watching television [β: 2.17 (95% CI: 1.39, 2.95); P-trend < 0.001]; furthermore, they had greater total energy intake [β: 160 (95% CI: 115, 210); P-trend < 0.001] and were less likely to follow a Mediterranean diet [OR: 0.55 (95% CI: 0.41, 0.73); P-trend < 0.001]. In conclusion, the association between OREB and obesity is biologically plausible because OREB are associated with energy intake and poor accordance with the Mediterranean diet. Studies on the association between OREB and obesity should control for the confounding effect of physical activity and sedentariness.