Objectives - Anorexia nervosa (AN) is a life-threatening mental health condition. A core feature is a disturbance of body image, such that sufferers see themselves as fatter than they actually are. Design - We tested the effectiveness of a novel training programme to recalibrate our participants’ perception of body size. Methods - In a novel adaptation of a cognitive bias training programme, participants judged the body size of a series of female bodies and were given feedback to improve their accuracy over four daily training sessions. In Study 1, we recruited young women with high concerns about their body size for a randomized controlled study. In Study 2, we then applied the training programme to a case series of women with atypical AN. Results - In Study 1, the training programme significantly improved the body size judgements of women with high body concerns compared to controls. We also found evidence of improved body image and reduced eating concerns in this group. In Study 2, the programme again recalibrated the body size judgements of women with atypical AN. We also saw evidence of a clinically meaningful reduction in their body size and eating-disordered concerns. Conclusions - This training has the potential to be a valuable treatment used together with more traditional talking therapies.