Browsing by Subject "Bariatric Surgery"

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    Assessment of Body Composition and Nutritional Status in Individuals with Obesity Before and in the Long-Term After Bariatric Surgery
    (2015-06) Cole, Abigail
    One of the most successful treatments for obesity is bariatric surgery. The Roux-en-Y gastric bypass (RYGB), in particular has been the most commonly performed bariatric surgery over the past decade. It is not well known how time will influence the broader inflammatory-related health outcomes of bariatric surgery, which may depend on complex inter-relationships between nutritional status and body fat mass (FM). This dissertation focuses on the long-term changes in nutritional status and body composition after RYGB with a particular focus on vitamins and minerals that have potential inflammatory action and the development of improved methods to assess changes in body composition in obese individuals. In Chapter 3 we report the results of a pilot study to assess long-term changes in body composition and nutritional and inflammatory status after RYGB. From the assessment of 5 women who were monitored over an 8.5-year period after RYGB we found that improvements in vitamin D status and potential improvements in inflammatory status can occur over time. However, continued loss of lean soft tissue (LST) occur on the background of weight regain between 1-year and 8.5-years post-RYGB. Losses of LST were correlated with decreased handgrip strength. In Chapter 4 we report the results of a validation study to compare the results of a new application of BIS based on multicomponent physiologic models with existing body composition data from DXA in a large NHANES dataset with 5470 observations and in a longitudinal dataset of 25 women for the first-year after RYGB. We found that the BIS method was in relatively good agreement with DXA for the assessment of FM and lean tissue, and that the BIS method was equally as good as DXA for assessing changes in FM in particular after RYGB, over the period from 6-months to 1-year. In the coming years, bariatric surgery is sure to remain a popular treatment for obesity and it is clear that we need better methods to assess changes in body composition in a more comprehensive way, in order to better understand the ramifications of these changes in light of long-term nutritionally relevant health outcomes, including inflammation. This dissertation could serve to inform future studies that should aim to tease apart the factors contributing to long-term FM gain, but more importantly loss of LST and muscle strength, to establish evidence based guidelines.
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    Changes in gastrointestinal hormones, leptin, and satiety after gastric bypass surgery
    (2012-06) Beckman, Lauren Marie
    The Roux-en-Y gastric bypass (RYGB) is a well-accepted tool for the treatment of obesity and compared to conventional weight loss methods (e.g. diet and exercise) and other weight loss surgeries (e.g. gastric banding), it results in considerable weight loss that is maintained long-term. Although successful, the mechanisms for weight loss are not completely understood and it is thought that favorable changes in several gastrointestinal (GI) hormones and satiety play a role. Previous research suggests that the satiety promoting hormones, GLP-1 and PYY increase after RYGB, while the orexigenic GI hormone ghrelin and the adipocytokine leptin decrease. These changes generally occur before substantial weight loss, suggesting that a component of the surgery is responsible. Subjective satiety has also been reported to increase after RYGB, likely because of changes in the GI hormones and due to the reduced stomach capacity after surgery, but it is not clear if this alteration is maintained long-term. In addition, it is currently not well understood what effect different macronutrients have on the GI hormones and subjective satiety in the post-RYGB patient population. From a clinical perspective, there is a need for understanding how various macronutrients affect these parameters, as this is useful information that might allow for improved dietary treatment recommendations after RYGB. In the first study, changes in the GI hormones and leptin were evaluated after RYGB. This study also assessed if the GI hormones differed after a short-term dose of protein (PRO-BEV) or fat (FAT-BEV). GLP-1, PYY, ghrelin, and leptin were assessed in 16 women before and at 2, 6, 26, and 52 weeks after RYGB. GLP-1 increased at Weeks 6 and 52 in the FAT-BEV group compared to before surgery. PYY remained elevated at Week 52 in the FAT-BEV group. Ghrelin decreased at Weeks 2, 6, and 52 in the PRO-BEV group compared with Pre-RYGB. Ghrelin was lower in the PRO-BEV group compared with the FAT-BEV group at Week 6. Fasted leptin decreased at all visits in both groups and was lower in the FAT-BEV compared with the PRO-BEV group at Week 52. In the second study, subjective satiety was evaluated before and after RYGB. This study also assessed if subjective satiety differed after a dose of either protein or fat and investigated if subjective satiety, the GI hormones, and/or weight loss are related. Subjective satiety was not different between treatment groups. Satiety increased at the Week 2 visit compared to before surgery. Satiety scores had generally returned to Pre-RYGB levels after the Week 6 visit. Subjective satiety was not related to any of the GI hormones. Weight loss was unrelated to subjective satiety and the GI hormones. Results from these studies indicate that favorable changes occur after RYGB for the GI hormones/leptin and subjective satiety; some differences were evident soon after surgery (ghrelin, leptin, subjective satiety) while others were maintained long-term (GLP-1, PYY, ghrelin, leptin). In response to a short-term stimulus, protein suppressed ghrelin and fat stimulated GLP-1 and PYY. Although we did not find a difference in subjective satiety between beverage groups, assessment of the macronutrient effect on satiety is a novel analysis in this patient population, and further work is needed to better define the post-RYGB nutrition recommendations. Continued research in this area that attempts to better understand dietary components that could ultimately lead to successful weight loss/maintenance is needed for proper nutrition care after RYGB.