Anorexia nervosa (AN) is a serious and often fatal illness. Despite decades of research, investigators have failed to adequately advance our understanding of the biological aspects of AN that could inform the development of effective interventions. Genome-wide association studies are revealing the important role of metabolic factors in AN, and studies of the gastrointestinal tract are shedding light on disruptions in enteric microbial communities and anomalies in gut morphology. In this opinion piece, we review the state of the science through the lens of the clinical presentation of illness. We project how the integration of rigorous science in genomics and microbiology, in collaboration with experienced clinicians, has the potential to markedly enhance treatment outcome via precision interventions. Shifting paradigms in understanding and treating ANAN rests squarely on the psyche-soma border; however, etiological theories and treatments have historically focused on psychological, family, and societal factors. A conceptual shift is underway. The latest genome-wide association study (GWAS; see Glossary) for AN [1] suggested reconceptualizing AN as a 'metabo-psychiatric disorder'. In addition to identifying eight significantly associated genomic loci, a rich panel of genetic correlations underscored the role of psychiatric, anthropometric, and metabolic factors in the etiology of this highly lethal disease.

During the COVID-19 pandemic, the eating disorder clinician community saw an increase in severity and number of people seeking care for eating disorders. Due to this, its even more important for those who work with people with eating disorders to understand the medical complications these people are at risk for. The special issue of the Journal of Eating Disorders provides a comprehensive look at medical complications and also makes apparent deficits in the scientific literature.

Anorexia nervosa (AN) is a complex mental health disorder that may result in life threatening medical complications if not properly treated. Refeeding and weight restoration are the primary goals of treatment in AN. A multidisciplinary team is essential during this process in order to properly monitor and address complications that can arise during refeeding. There are benefits and drawbacks to different approaches to refeeding and weight restoration, however, recent research supports more aggressive approaches to refeeding and weight restoration. This review explores recommendations for methods of refeeding from various professional organizations, current standards of practice, as well as management of complications that may arise during the refeeding process. Abbreviations and symbols IntroductionThe Diagnostic and Statistical Manual of Mental Disorders, 5 th Edition defines anorexia nervosa (AN) as the restriction of energy intake relative to requirements leading to significantly low body weight, in conjunction with an extreme fear of gaining weight and a distorted view of body weight and shape [1]. AN is defined as either restricting type (AN-R) or binge-eating/purging type (AN-BP). AN-R occurs "when weight loss is accomplished primarily through dieting, fasting and/or excessive exercise". AN-BP is diagnosed "when during the last three months the individual has engaged in recurrent episodes of binge eating or purging behavior (i.e., self-induced vomiting or misuse of laxatives, diuretics, or enemas)" The severity of AN is defined by body mass index (BMI): mild: BMI > 17 kg/m 2 , moderate: BMI 16-16.99 kg/ m 2 , severe: BMI 15-15.99 kg/m 2 , and extreme: BMI <15 kg/m 2 .The overall prevalence of AN is estimated to be 1-2% of females between the ages of 15-35. Males have a rate of 0.1% and the overall female to male ratio is 1:20 [2][3][4]. AN has the highest mortality rate of any psychiatric disorder, with a reported mortality rate of 5.6% [5]. Medical complications related to the disorder result in 50% of the deaths in individuals with AN, and at least half of the remainder of the deaths have resulted from suicide. The peak occurrence of AN is during adolescence and early adulthood. Longitudinal studies have identified body dissatisfaction, dieting and picky eating as possible predictors for eating disorders. Additionally, multivariate studies have found obsessive-compulsive personality disorder as well as generalized anxiety indicate to have a strong predictive value for AN [3].