Discussion
muscle mass, eating behavior, gastrointestinal symptoms, shakes, fat-free mass loss, weight loss
OBESE, POSTOPERATIVE COMPLICATIONS
This study will be the first RCT specifically designed to assess the effect of protein supplementation in the form of a clear protein powder shake after bariatric surgery, more specifically after laparoscopic Roux-en-Y gastric bypass (RYGB). The primary endpoint is the percentage of fat-free mass loss after 6 months. This is defined as the fat-free mass loss as a percentage of total weight loss.This study is conducted in a highly specialized center for bariatric surgery. Study assessments are done by an experienced team consisting of bariatric surgeons, medical doctors, physical assistants, nurse practitioners, dieticians, and psychologists.The study is diligently designed to supply valuable data for this patient group. However, some challenges are faced inherent to this patient group. Like most clinical trials, the applicability of study results relies on the compliance of study participants.Reiber et al. found that many bariatric patients are non-compliant to follow-up after bariatric surgery [This non-compliance to follow-up may result in dropout of participants in our study as well. However, the center conducting the study has shown to be able to keep patients in follow-up after bariatric surgery very well, especially the first years, according to annual auditing data (DATO). The low number of patients lost to follow-up after surgery in our center is achieved by a periodic check of all patients in follow-up and their future appointments. If this check shows that patients have missed or canceled their appointments, they are being actively approached to schedule new visits to the hospital. This is standard practice in our center in order to minimize the amount of patients lost to follow-up after surgery.A recent study by Steenackers et al. assessed compliance to multivitamin supplementation after bariatric surgery. They found that only 24.9% of all patients reported high compliance whereas 17.8% did not take any multivitamins at all, despite extensive recommendations on this subject [Smelt et al. also found that adherence to multivitamins after bariatric surgery was poor. They identified several potential causes for it of which the most important were eating behavior, postoperative complications leading to gastrointestinal symptoms, treatment complexity, composition of multivitamins, and costs of multivitamin treatment [To reduce the influence of poor compliance, some precautions have been taken in the design of this study. All patients are screened before surgery to examine their eating behavior. If there are deficiencies in these behaviors, such as lack of regularity or too low an eating frequency, for example, patients are referred to a preparatory course with a dietician before surgery is scheduled. To lower treatment complexity, the use of a daily shake was chosen instead of one that must be used more often in a day. Furthermore, the shakes are packaged per portion and participants will receive a special shaker bottle which makes it easy to prepare the shake. Specifically, a clear shake is used instead of a milk-based shake because the composition of a clear shake is thought to be tolerated better after bariatric surgery because of changed food preferences [Costs will have no bearing on the compliance since study products are provided for free. The potential consequence of costs must however be a concern gets the supplementation gets implemented in future standard postoperative care.The team is trained to motivate study participants to be compliant to the shakes. Nonetheless, lack of compliance despite this motivational counseling, might be valuable information as well. Therefore, compliance is investigated using a calendar to monitor the compliance. Study participants will write down whether they used the study product that day fully, partly, or not at all. Study participants are encouraged to fill in this calendar honestly, rather than socially desirable. Next to the calendar, questionnaires are conducted to investigate reasons for (in)compliance.Paradis et al. wrote about bias in surgical trials and the effect it has on the internal and external validity of research [First of all, the risk of sampling bias must be reviewed because it may affect the generalizability of the results and thus external validity. This form of bias might occur when patients who are relatively active, are more prone to participate in the study because they are more interested in their own muscle mass. Physical activity is considered a potential confounder because it affects muscle mass in obese adults as described by Willis et al. [Interpatient variability in compliance to the postoperative protocol could also result in sampling bias. More compliant participants might also follow the dietary counseling for high-protein food products more carefully than less compliant participants. This might lead to a higher total protein intake, not necessarily as a result of the additional protein shake. Hence, results must also be corrected for total dietary protein intake. This will be measured by a 3-day food diary at the time of body composition assessments. This method was chosen as it minimalizes recall bias and takes variations between week- and weekend days into account [Another risk of bias, more specifically attrition bias, is arising from the use of a placebo in the control group. In this study, maltodextrine is used as the main ingredient to create an isocaloric alternative for the protein drink. Maltodextrine itself could affect body composition and in that way become a confounder. Other nutrients that could be used to add calories are fat or alcohol. However, fat is not easily soluble in a clear shake and alcohol is obviously undesirable from the medical perspective. For this reason, maltodextrine is considered the best comparator in this study design.Lastly, transfer bias might occur when the protein drink or the placebo is tolerated better than the other product leading to excessive dropout in one of the study groups. To minimize this form of bias, the team is trained to encourage patients’ compliance to follow-up.The study design is adapted to these calculated risks of bias. Therefore, reliable and generalizable results are expected. The results will be published and presented at international congresses and might hopefully lead to further research and thus improvement of care of bariatric surgery patients.