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Metabolic Impact of Dietary Protein Supplementation in Surgical Weight Loss

Final Report Summary - MIPS (Metabolic Impact of Dietary Protein Supplementation in Surgical Weight Loss)

Over the last decade, the number of bariatric surgery (BS) procedures performed worldwide has greatly increased [1, 2]. This is not only because of the increasing global prevalence of obesity [3] but also because of the increasing recognition of the many health benefits associated with BS [2,4]. BS is the most effective therapy for weight loss and for treatment of comorbidities associated with obesity [5]. The increase in popularity of BS is based on its efficacy and the low rates of surgical complications. However, vitamin mineral and protein deficiencies may potentially develop. Safe evidence-based dietary recommendations for use during calorie restriction – either by diet and/or by BS – are extremely important to develop. Dietary protein (PRO) is the key to maintaining lean body mass and promoting weight maintenance. Although guidelines and clinical practice recommend protein supplementation, there is currently no evidence-based data on protein supplementation after BS. Furthermore, no randomized control trials in the BS patient population currently exist to targeting the establishment of the quantity and/or quality of dietary protein that should be prescribed in the short and long term after BS, to maintain a healthy nutritional and metabolic status.

This pilot study investigated the effects of a 3 month-protein supplementation regimen during surgical weight loss. We tested 2 different level of PRO supplementation (standard and high), as well as the carry-over effect of the intervention at 9 months. We investigated the safety and effect of PRO supplementation during weight loss on glucose homeostasis, satiety, nitrogen balance, lean body mass preservation, and total daily energy expenditure. Two important unresolved questions are the quantity of protein supplementation that should be administered, and the duration of the protein supplementation after BS. These are not trivial questions as it is difficult to get patients to increase their protein intakes, particularly if levels are set unnecessarily high. There is also a lack of consensus, and of data, on the long term duration of protein supplementation after BS. Of note, after the immediate weight loss phase post BS, weight regain is commonly observed, specifically 24 months after surgery. In addition to inappropriate lifestyle, lower resting energy expenditure (REE) and loss of fat free mass (FFM) after surgery has been shown to be the risk factors for weight regain. Changes in intestinal hormones [6] and inflammatory cytokines [7] have also been considered to promote weight loss, alter body composition, and possibly modulate food intake [8]. In summary, long term weight regain and low-protein intake are common after BS. Specific recommendations in terms of dietary protein supplementation need to be defined as they may have an impact on long-term health outcomes after BS.

This study was a pilot study (due to budget constrictions) and was designed to address feasibility and to collect prelimninary data to design a larger scale study. With pilot data we are unable to make clinical recommendations. In this randomized pilot study, we successfully obtained preliminary data on the effect of weight loss and PRO supplementation over each of our specifics study aims: (Aim1), nitrogen balance, by quantify nitrogen input (intake) and output (specimens) during the inpatient study (Aim 2), lean body mass, fat mass, total body water, also, after a meal test, we tested resting energy expenditure, and diet induced thermogenesis (Aim 3) hormone (PYY, GLP-1) and perceived (visual analogue scale) satiety over the study; (Aim 4) serum levels of branched chain amino acids.

The main successful outcome of this study protocol is that we were able to design and validate a rigorous methodology for examining the aims described above. As a result of having successfully implementing the methods designed in this protocol, we will be able to develop of a follow-up MIPS as Randomized Control Trial with a higher number of subjects. This future proposal will significantly contribute to the development of the evidence-based nutritional guidelines for clinical practice for moderately and severely obese individuals undergoing BS at short and long term follow-up.

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