Achalasia cardia, a primary motility disorder of the esophagus, poses significant malnutrition risks. This study aims at comprehensively assessing the nutritional status in untreated achalasia patients, contrasting it with functional gastrointestinal disorders (FGIDs) cases and impact of per-oral endoscopic myotomy (POEM) on nutrition at one-year. We conducted a prospective study, including consecutive achalasia cases, from December 2021 to April 2022 at a tertiary care centre. Biochemical parameters, anthropometry, subjective global assessment (SGA) and malnutrition universal screening tool were used for nutritional assessment. Cases diagnosed with FGIDs served as controls. As many as118 cases (41.2 ± 13.9years, 61% males) with achalasia and 200 controls (43.4 ± 11.9years, 69% males) were included in the study. Sub-types of achalasia included type I (16.9%), II (76.3%) and III (6.8%). Overall, 38.1% and 6.8% cases were moderately and severely malnourished, respectively. As compared to controls, cases with achalasia had lower pre-albumin (19.4 vs. 25.2; p = 0.001), serum calcium (p = 0.012), vitamin D (p = 0.001), serum iron (p = 0.001), triceps fold thickness (p = 0.002) and hand-grip strength (p = 0.001). On univariate analysis, type-I achalasia, body mass index, % weight loss, lower esophageal sphincter pressures and Eckardt scores were predictors of malnourishment (SGA). On multivariate analysis, type of achalasia, mid arm circumference and low body mass index were significant predictors of malnourishment in cases with achalasia. There was significant improvement in the nutritional status after POEM at one-year follow-up. Achalasia patients demonstrate a notably higher risk of malnutrition compared to individuals with FGIDs. Nutritional status significantly improves after POEM. (NCT05161923).