Methods: MEDLINE surveys were carried out and reference lists were cross-checked to identify publications on long-term outcome for dietary treatment of obesity. 898 papers were identified, 17 fulfilled our planned criteria for inclusion (dietary treatment; adults; follow-up period ≥ 3 years; follow-up rate ≥ 50% of original study group; information on one of the success criteria: maintenance of all weight initially lost (or further weight reduction) or maintenance of at least nine to 11 kg of initial weight loss; obesity complications of the patient group not over-represented; English, German or Scandinavian languages). Results: The 17 included publications (hereof three publications on randomized clinical trials with control group relevant for this review) reported on 21 study groups, comprising 3030 patients. Of these 2131 (70%) were followed-up for 3–14 years (median 5 years). Mean initial weight loss ranged from four to 28 kg (median 11 kg). Overall, 15% (median, range 0–49%) of followed-up patients fulfilled one of the criteria for success. Overall, success rates seemed stable for up to 14 years of observation. Diet combined with group therapy lead to better long-term success rates (median 27%) than did diet alone (median 15%) or diet combined with behaviour modification (median 14%). Active follow-up was generally associated with better success rates than was passive follow-up (19% vs. 10%). Conventional diet seemed to be most efficacious in addition with group therapy, whereas VLCD apparently was most efficacious if combined with behaviour modification and active follow-up. Conclusion: The literature on long-term follow-up of dietary treatment of obesity, although limited and inhomogeneous, points to an overall median success rate of 15% and a possible adjuvant effect of group therapy, behaviour modification and active follow-up.