Rationale: Protein malnutrition is a severe complication of bariatric surgery and leads to
increased morbidity. Previous studies have shown that protein intake and physical activity
are the most important factors in the preservation of fat free mass during weight loss. Low
protein intake is very common in patients undergoing bariatric surgery despite dietary
counselling. Protein powder supplements might help patients to achieve the protein intake
recommendations after bariatric surgery and could therefore contribute to preserve fat free
mass.
Objective: The main aim of this study is to assess the effect of a daily consumed clear
protein powder shake during the first six months after bariatric surgery on fat free mass
loss in the first twelve months after laparoscopic Roux-en-Y gastric bypass (LRYGB).
Study design: Double-blind randomized placebo-controlled intervention study
Study population: Patients undergoing LRYGB at the bariatric expertise center for obesity of
the Maasstad Hospital Rotterdam.
Intervention and procedure: Inclusion will take place at the outpatient clinic of the
bariatric expertise center for obesity of the Maasstad Hospital. Patients will be randomly
assigned to either the intervention or control group before surgery. The intervention group
will receive a clear protein powder shake of 200 ml containing 20 grams of whey protein which
should be taken daily during the first six months after LRYGB. The control group will receive
an isocaloric, clear, placebo shake containing maltodextrine.
Main study parameters/endpoints: The main study parameter is the percentage fat free mass
loss six months after surgery, calculated as fat free mass loss (kg) divided by total weight
loss (kg) x 100%. Fat free mass will be assessed by multi-frequency bioelectrical impedance
analysis (MF-BIA). Secondary parameters are percentage fat free mass loss, total weight loss,
fat mass loss, BMI, hand grip strength, total protein intake and its progression over time,
measured at baseline, 3, 6 and 12 months of follow-up.
Nature and extent of the burden and risks associated with participation, benefit and group
relatedness: No additional outpatient visits will be required for study participants. A three
day food diary and physical activity questionnaire must be filled out by all study
participants at five regular follow-up moments. Body composition and handgrip strength will
be assessed during these visits. All study participants will be asked to drink a daily shake,
either protein or placebo, integrated in their postoperative diet. Study participants will
receive information about the changes in body composition after surgery which is considered
to be a significant benefit for patients participating in this study. The risk of
participation is considered low. The risk consists of a possible allergic reaction to either
the protein shake or the placebo.
