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 > or = 3 years; follow-up rate > or = 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 (here of 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.