The study of more than 5,000 women in their 40s and 50s found 3% had an active eating disorder in mid-life.
The researchers said the figure was surprisingly high, as eating disorders are primarily associated with adolescence or early adulthood.
The researchers have called for raised awareness about eating disorders affecting this age group and said it is imperative health professionals begin to understand their reasons for not coming forward.
Around 15.3% of women in the study reported having an eating disorder at some point in their life and 3.6% reported an eating disorder in the past 12 months.
Less than 30% of women who had eating disorders said they had sought help or received treatment.
Dr Nadia Micali, lead author from University College London, said: “Our study shows that eating disorders are not just confined to earlier decades of life and that both chronic and new onset disorders are apparent in mid-life.
“Many of the women who took part in this study told us this was the first time they had ever spoken about their eating difficulties, so we need to understand why many women did not seek help.
“It may be that there are some barriers women perceive in healthcare access or a lack of awareness among healthcare professionals.”
The researchers also assessed factors that may be associated with the onset of an eating disorder including childhood happiness; parental divorce or separation; life events; relationship with parents; and sexual abuse.
Dr Micali explained: “The early risk factors we assessed were associated with different eating disorders.
“Anorexia, bulimia, binge eating and purging disorder were all associated with childhood unhappiness, and parental separation or divorce during childhood seemed to increase the risk of bulimia, binge eating disorder and atypical anorexia.
“We also found that death of a carer could increase the likelihood of purging disorder and that sexual abuse during childhood, or a fear of social rejection, was associated with all eating disorders.”
In this study a woman’s risk of suffering from anorexia nervosa or bulimia nervosa, two of the most common eating disorders in the UK, was increased by 4-10% per unit score of ‘unhappiness’ if they reported being unhappy during childhood.
Higher interpersonal sensitivity – the ability to accurately assess others’ feelings - was associated with an increased risk of binge eating by 19% per unit score of ‘sensitivity’. A good mother–daughter relationship was associated with a 20% reduced chance of developing bulimia.
The researchers gathered their data using a previous University of Bristol study, where women answered a questionnaire on their past life experiences, including eating disorders.
The researchers of the latest study said more research is needed into the topic, as the University of Bristol study took a sample of women from one area of the UK, so the results may not be accurate for the whole country.
They added that the data in this study covered the last 40 years and might reflect the past, rather than the current lack of clinical awareness of eating disorders in the UK.