The purpose of our study is to establish if the proportion of patients diagnosed with anorexia nervosa that have a history of excess weight has increased over a 10-year period and to study how different premorbid weight groups vary in terms of clinical characteristics. We performed a single-center, retrospective cohort study of all new patients presenting with anorexia nervosa, restrictive and binge/purge subtypes, in 2004 and 2014 at the Adolescent Medicine Clinic of Sainte-Justine University Health Centre (n = 172). The prevalence of excess premorbid weight was similar in both cohorts (32% in 2004 versus 29.5% in 2014). The historically overweight subgroup had a lower heart rate at intake (64.77 versus 69.75, p = 0.03). Patients with excess premorbid weight lost an average of 1 kg more per month than their historically thinner counterparts (2.6 kg versus 1.6 kg/month, p = 0.0011). The total decrease in BMI was much greater in patients with a history of excess weight (7 BMI points versus 3.8, p = 0.0001).Conclusion: Since overweight and obese patients present with significant weight suppression values, our study stresses the importance of screening for AN in all patients rather than in only the noticeably underweight. What is Known: • More than one third of patients presenting with AN have a history of overweight or obesity, which is comparable to the general population. • A delay between AN onset and diagnosis has been described in overweight adolescents. What is New: • Historically overweight patients presenting with AN demonstrate increased speed of weight loss, greater drop in BMI, and lower heart rate at presentation. • For patients with a history of excess weight considered as having recovered from AN, the average BMI at discharge was within normal limits.