BACKGROUND: Nonadherence to follow-up after bariatric surgery is associated with lower long-term weight loss. Yet limited data exists on the youngest bariatric population, adolescents and young adults (AYA), who experience life changes in social, psychological, and behavioral domains that can interrupt follow-up. To better understand how age groups affected health outcomes in these populations, this study compared bariatric clinic follow-up adherence between AYA and assessed the impact of follow-up interruption on weight loss. METHODS: Using an institutional registry, we retrospectively reviewed adolescents (age 14-18) and young adults (YA) (age ≥19-26) who underwent sleeve gastrectomy between January 2018 and May 2023. Primary outcome was follow-up compliance (1, 3, 6, 12, 18, 24 months). Secondary outcomes included median total weight loss percentage (%TWL). Lost to follow-up (LTF) was determined by the last bariatric clinic visit attended. RESULTS: Of 73 (46.8%) adolescents and 83 (53.2%) YA, median preoperative BMI was higher in adolescents (51.0 [44.5,56.8] vs. 48.5 [43.4,51.7], p = 0.015). Median total weight loss percentage (%TWL) was greater in YA up to 6 months postoperatively (23.3 [20.5,27.4] vs. 20.2 [15.1,24.9], p = 0.008) but did not differ afterward. Median missed follow-up appointments were similar between adolescents (3[3,4]) and YA (4[3,4]). Adolescents were more likely to be LTF at 6 months (34.3% vs. 20.5%, p = 0.053). Patients in both age groups were more likely to be LTF if %TWL was in the lowest tertile at 6 months (OR 4.78, 95% CI [2.04, 11.18], p = <
0.002) or 1 year (OR 18.45, 95% CI [5.75, 59.2], p <
0.002). CONCLUSIONS: Clinic adherence in the post-bariatric AYA population is poor especially among patients with less %TWL. Identifying when AYA are at risk of LTF allows for targeted interventions to maximize adherence and potentially improve long-term health.