<b><i>Aim</i></b>: The purpose of this study was to identify psychosocial determinants for maintaining weight loss. <b><i>Methods</i></b>: 42 obese individuals who achieved a 12% weight loss before entering a 52-week weight maintenance program were interviewed qualitatively. Psychosocial factors related to weight loss maintenance were identified in two contrasting groups: weight reducers and weight regainers. Groups were defined by health-relevant weight maintenance (additional weight loss > 3% at week 52, n = 9 versus weight gain > 3%, at week 52, n = 20). <b><i>Results</i></b>: Weight reducers reported structured meal patterns (p = 0.008), no comfort eating (p = 0.016) and less psychosocial stress (p = 0.04) compared to weight regainers. The ability to instrumentalize eating behavior emerged as an important factor (p = 0.007). Nutritional knowledge, motivation or exercise level did not differ between groups (p > 0.05). <b><i>Conclusions</i></b>: Successful weight loss maintenance was associated with an interplay between behavioral, affective and contextual changes. ‘Instrumentalization of eating behavior' seems to be an important element in long-term weight maintenance.