Objective To describe the relationship between long-term weight loss (LTWL) success and lifestyle behaviours among US adults. Design Serial cross-sectional data from National Health and Nutrition Examination Survey cycles 2007-2014. Setting and participants Population-based nationally representative sample. The analytic sample included 3040 adults aged 20-64 years who tried to lose weight in the past year. Measures Participants were grouped into five LTWL categories (<5%, 5%-9.9%, 10%-14.9%, 15%-19.9% and ≥20%). Lifestyle-related behaviours included the following: alcohol intake, physical activity, smoking, fast-food consumption, dietary quality (Healthy Eating Index (HEI)) and caloric intake. Multivariable regression was employed adjusting for age, sex, race/ethnicity, marital status, education, household income and size, current body mass index and self-reported health status. Results Individuals in the 15%-19.9% LTWL group differed significantly from the reference group (<5% LTWL) in their physical activity and dietary quality (HEI) but not caloric intake. Specifically, they had a higher HEI score (β=3.19; 95% CI 0.39 to 5.99) and were more likely to meet physical activity guidelines (OR=1.99; 95% CI 1.11 to 3.55). In comparison, the ≥20% LTWL group was significantly more likely to smoke (OR=1.63; 95% CI 1.03 to 2.57) and to consume lower daily calories (β=-202.91; 95% CI -345.57 to -60.25) than the reference group; however, dietary quality and physical activity did not significantly differ. Conclusion Among a national sample of adults, a higher level of LTWL success does not necessarily equate to healthy weight loss behaviours. Future research should attempt to design interventions aimed at facilitating weight loss success while encouraging healthy lifestyle behaviours.