Patients who have scheduled a gastric bypass (RYGB) in UZ Leuven, will be questioned preoperatively and one, three, six and twelve months after gastric bypass surgery. The purpose of this study is to explore current practice regarding the use of medication and medication counseling after RYGB and to examine the changes in dietary pattern before and after RYGB.

Target group: patients who have scheduled a gastric bypass in UZ Leuven. Patients will be questioned preoperatively and one, three, six and twelve months after gastric bypass surgery. Each assessment will be performed during a routine consultation.

The following aspects will be investigated:

• Medication The investigators have composed a questionnaire to examine which drugs the patients use, adherence, information received about medication and from whom,…
• Clinical parameters Every consultation, concentrations of hemoglobin, iron, hepcidin, vitamin B12,…. and a 24h urine collection to determine calcium excretion will be collected.
• Dietary intake The investigators will ask patients to keep a food record during two non-consecutive days preceding each consultation. In this food record patients have to note all consumed foods and beverages with the right/estimated amounts. This makes it possible to see the changes of the composition of the meals before and after RYGB.
• Body composition

Inclusion Criteria:

• Patients who have scheduled gastric bypass
• Use of at least one chronic drug (including contraception)

Exclusion Criteria:

• Patients who have undergone another form of bariatric surgery before RYGB

Patients who have scheduled a gastric bypass