There is a paucity of studies on the frequency of binge-eating disorder (BED) and nocturnal eating (NE) and their potential role as barriers in non-surgical weight loss treatment in subjects with severe obesity (body mass index [BMI] ≥35 kg m ). The aim was to identify BED and NE, and their effect on weight loss treatment. In total, 1132 (727 women, 405 men), BMI ~41 kg/m were patients in a 12-month weight loss programme at a specialist clinic. The questionnaire for eating and weight patterns-revised was completed by the patients before start of treatment. BED was diagnosed in 5.1% of men and 12.4% of women. NE prevalence was 13.5% and 12.7%, respectively. Mean (±SEM) 12-month weight loss was less in patients with NE compared to those without (-11.0 ± 1.5 vs -14.6 ± 0.7 kg, P = .008) but did not differ in patients with and without BED, (-12.3 ± 1.9 vs -14.2 ± 0.6 kg, P = .24). Factors associated with dropout were BED (odds ratio, OR 1.57, 95% confidence interval (CI) 1.14-2.17; P = .006) and previous weight loss attempts (OR 1.35, 95% CI 1.0-1.7; P = .02). BED did not seem to hinder weight loss whereas NE resulted in less weight loss in patients with severe obesity who completed a 12-month treatment programme. Previous weight loss attempts affect both dropout and ability to lose weight.