Assessment of Body Composition and Nutritional Status in Individuals with Obesity Before and in the Long-Term After Bariatric Surgery

Abstract

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.