We evaluated changes in sexual quality of life as they relate to weight loss over a 2-year period in individuals undergoing weight loss treatment. Six dimensions of sexual quality of life were measured using items from the Impact of Weight on Quality of Life questionnaire (feeling sexually unattractive, lacking sexual desire, reluctance to be seen undressed, difficulty with sexual performance, avoidance of sexual encounters and lack of enjoyment of sexual activity). At baseline women were more likely than men to report lack of sexual enjoyment and reluctance to be seen undressed in spite of lower body mass index (BMI). Weight loss averaged 13.1% and was significantly associated with improvements in all sexual quality of life dimensions. A 3-4% regain did not appear to negatively affect sexual quality of life. The greatest improvements for women had occurred by 3 months and were observed in all dimensions, whereas for men only 'not feeling sexually attractive' showed marked improvement in this short time frame.