Bariatric surgery, gastric bypass, sleeve gastrectomy, or similar procedures, triggers telogen effluvium in approximately 50% of patients, typically appearing 3–6 months postoperatively. The driver is rapid weight loss combined with reduced micronutrient absorption from the altered gut anatomy. The pattern resembles standard telogen effluvium clinically but the recovery trajectory differs.

A 5-year follow-up cohort published in 2023 tracked 412 post-bariatric patients. Hair density at 5 years had returned to baseline in 71% of patients. The remaining 29% had persistent thinning, with strongest correlation to baseline vitamin D status, ferritin recovery, and protein intake during the rapid weight loss phase. Long-term zinc and selenium status also tracked with hair outcomes more than acute studies had suggested.

Practical implications: bariatric patients benefit from aggressive nutritional monitoring during the first 18 months postop. Adequate protein (1.5g/kg adjusted ideal body weight), iron and ferritin tracking every 3 months, vitamin D supplementation to 50+ ng/ml, and zinc levels checked annually. For patients with established post-bariatric hair loss, addressing identified deficiencies typically restores hair density within 9–12 months, though acceleration of any underlying pattern hair loss can persist.