Objective: To identify prognostic metabolic and hormonal markers for long-term weight loss outcome in obese women. Design: Dietary intervention consisting of 36 weeks treatment by a 4.2 MJ/d low-fat high carbohydrate diet, and follow-up 2 1/2 years after termination of treatment. Setting: Outpatient clinic in Copenhagen. Subjects: Forty consecutive female obese patients aged 15 to 62 years. Main outcome measure: Weight loss. Results: The maximum weight loss (mean 16.2 kg, 95% CI 14.2-18.2) was positively associated to pre-treatment 24-h energy expenditure (P < 0.01), fat oxidation (%) (P < 0.02), plasma dihydrotestosterone (DHT) (P < 0.01), and to postprandial noradrenaline concentration (P < 0.04). Together these factors could explain 41% of the variation in maximum weight loss. Only 24-h EE and DHT had predictive power on weight loss after 36 weeks. Weight losses in upper and lower tertiles of DHT concentrations were 17.7 kg (14.1-21.4) and 9.8 kg (6.2-13.3) (P < 0.02). The adjusted relative risk of losing < 10 kg in the upper compared to the lower DHT tertile was 12% (4-32%). At 2 1/2 y follow-up 21 patients had maintained some of the weight loss (54%), while 14 patients had maintained > 5 kg weight loss (36%). High levels of pre-treatment DHT were also associated with better weight loss at 2 1/2 y follow-up. Conclusion: The study suggests that in particular DHT, but also 24-h EE, fat oxidation, and plasma noradrenaline, may be prognostic markers for weight loss outcome in obese women.