Not merely a question of self-control: The longitudinal effects of overeating behaviors, diet quality and physical activity on dieters' perceived diet success.

This longitudinal study was conducted between 2010 (T1) and 2014 (T2) on a random sample from the general Swiss population (N = 2781, 46% male). Results showed that dieters (restrained eaters) who reported lack of success in T2 were overweight in T1, had higher levels of emotional and external eating, overeating, and ambivalence toward eating palatable food in T1, and a significantly increased body mass index (BMI) in the period between T1 and T2. Dieters who reported success in T2 had maintained a normal BMI between T1 and T2, had a higher diet quality in T1 and had maintained regular physical activity for at least one year before T2. The logistic regression revealed that high levels of dispositional self-control provided the most important predictor of being a successful dieter. When controlling for dispositional self-control, high levels of emotional eating, overeating, and ambivalence in T1, together with increases in these levels between T1 and T2, were associated with a decreased likelihood of being a successful dieter in T2. High levels of diet quality in T1 and the maintenance of regular physical activity were associated with an increased likelihood of being a successful dieter in T2. Results suggest that diet success and failure is a long-term phenomenon, partly but not fully explained by dispositional self-control. Independent of self-control persistent patterns of overeating due to emotional eating and ambivalent feelings toward eating palatable food, also explain long-term diet failure. A high diet quality and maintenance of regular physical activity accounted for dieters' long-term success. This is the first study that examined the long-term psychological and behavioral characteristics of successful and unsuccessful restrained eaters.