[Nutritional follow-up after gastric bypass].

Roux-en-Y gastric bypass has become one of the main bariatric procedures. This surgical operation shows excellent results in weight evolution and quality of life and allows a decrease of mortality. However, it leads, relatively often, to nutritional deficiencies which need an effective post-operative follow-up. This follow-up includes not only medical and dietetic encounters but also regular blood analyses made every 3 months during the first post-operative year, every 6 months the second year, then each year. The most frequent deficiencies are those in vitamin B12, iron and folic acid. The secondary hyperparathyroidism characterized by an increase of PTH associated to a low vitamin D and a normal calcium, is quite frequent.