Long-Term Body Composition Changes in Women Following Roux-en-Y Gastric Bypass Surgery.

BACKGROUND: Although most individuals experience successful weight loss following Roux-en-Y gastric bypass (RYGB), weight regain is a concern, the composition of which is not well documented. Our aim was to evaluate changes in body composition and handgrip strength as a measure of functional status in participants from a previous 1-year post-RYGB longitudinal study who had undergone RYGB approximately 9 years prior. METHODS: Five women from an original larger cohort were monitored pre-RYGB and 1.5 months, 6 months, 1 year, and 9 years post-RYGB. Body composition was assessed at all time points using dual energy x-ray absorptiometry and multiple dilution. Handgrip strength was measured using a digital isokinetic hand dynamometer (Takei Scientific Instruments, Ltd, Tokyo, Japan). RESULTS: Mean time to final follow-up was 8.7 years. Lean soft tissue (LST) loss over the ~9-year period was on average 11.9 ± 5.6 kg. Compared with 1-year post-RYGB, 9-year LST was 4.4 ± 3.0 kg lower ( P = .03). Fat-free mass decreased over the 9-year period by 12.6 ± 5.8 kg. Mean fat mass (FM) decreased from 75.4 ± 22.6 kg pre-RYGB to 35.5 ± 21.5 kg 1 year post-RYGB but then trended toward an increase of 8.6 ± 7.0 kg between 1 year and 9 years post-RYGB ( P = .053). Loss of LST was correlated with loss of handgrip strength ( r = 0.64, P = .0005). CONCLUSION: The continued loss of lean mass associated with decreased handgrip strength occurring with long-term trend toward FM regain post-RYGB is concerning. The loss of LST and functional strength carries particular implications for the aging bariatric population and should be investigated further.

Phase Angle and Impedance Ratio: Reference Cut-Points From the United States National Health and Nutrition Examination Survey 1999-2004 From Bioimpedance Spectroscopy Data.

BACKGROUND: Raw bioimpedance parameters (eg, 50-kHz phase angle [PA] and 200-kHz/5-kHz impedance ratio [IR]) have been investigated as predictors of nutrition status and/or clinical outcomes. However, their validity as prognostic measures depends on the availability of appropriate reference data. Using a large and ethnically diverse data set, we aimed to determine if ethnicity influences these measures and provide expanded bioimpedance reference data for the U.S. METHODS: The National Health and Nutrition Examination Survey (NHANES) is an ongoing compilation of studies conducted by the U.S. Centers for Disease Control and Prevention designed to monitor nutrition status of the U.S. POPULATION: The NHANES data sets analyzed were from the years 1999-2000, 2001-2002, and 2003-2004. RESULTS: Multivariate analysis showed that PA and IR differed by body mass index (BMI), age, sex, and ethnicity (n = 6237; R2 = 41.2%, P < .0001). Suggested reference cut-points for PA stratified by age decade, ethnicity, and sex are provided. CONCLUSION: Ethnicity is an important variable that should be accounted for when determining population reference values for PA and IR. We have provided sex-, ethnicity-, and age decade-specific reference values from PA for use by future studies in U.S. POPULATIONS: Interdevice differences are likely to be important contributors to variability across published population-specific reference data and, where possible, should be evaluated in future research. Ultimately, further validation with physiologically relevant reference measures (eg, dual-energy x-ray absorptiometry) is necessary to determine if PA/IR are appropriate bedside tools for the assessment of nutrition status in a clinical population.

The Influence of Bariatric Surgery on Serum Bile Acids in Humans and Potential Metabolic and Hormonal Implications: a Systematic Review.

Recent research suggests a mechanistic role for bile acids (BA) in the metabolic improvement following bariatric surgery. It is believed that the hormonal and metabolic effects associated with changes in systemic BAs may be related to the farnesoid X receptor (FXR) and a G-protein coupled receptor (TGR5). This systematic review examines changes in systemic BAs following bariatric procedures. Studies were included if they reported the measurement of systemic BAs in humans at at least one time point after bariatric surgery. Eleven papers were identified that met the inclusion criteria. Seven studies reported the effect of Roux-en-Y gastric bypass (RYGB) on fasting BAs. The majority (6/7) reported that fasting BAs increased after RYGB. Data regarding fasting BAs after vertical sleeve gastrectomy (VSG) and laparoscopic gastric banding (LAGB) are inconsistent. Data regarding post-prandial BA changes after RYGB, VSG, and LAGB are also inconsistent. More research is needed to investigate the connection between BAs and the metabolic improvement seen after bariatric surgery.

Bioimpedance at the bedside: current applications, limitations, and opportunities.

The loss of muscle mass is a defining characteristic of malnutrition, and there is ongoing interest in the assessment of lean tissue at the bedside. Globally, bioimpedance techniques have been widely appreciated for their noninvasiveness, safety, ease of use, portability, and relatively low cost compared with other clinically available methods. In this brief update, we review the 3 primary types of commercially available bioimpedance devices (single- and multiple-frequency and spectroscopy) and differentiate the underlying theory and current applications of each. We also address limitations and potential opportunities for using these devices at the bedside for clinical assessment. Mixed reports in the validation literature for all bioimpedance approaches have raised questions about absolute accuracy to estimate whole body composition in clinical populations, particularly those with abnormal fluid status and/or body geometry in whom underlying method assumptions may be violated. Careful selection of equations can improve whole body estimates by single- and multiple-frequency techniques; however, not all devices will allow for this approach. Research is increasing on the use of bioimpedance variables including phase angle and impedance ratio as potential markers of nutrition status and/or clinical outcomes; consensus on reference cut-points for interpreting these markers has yet to be established. Novel developments in the bioimpedance spectroscopy approach are allowing for improved fluid management in individuals receiving dialysis; these developments have implications for the clinical management of other conditions associated with fluid overload and may also provide enhanced whole body estimates of lean tissue through new modeling procedures.

Vitamin D status following bariatric surgery: implications and recommendations.

Individuals with extreme obesity who qualify for bariatric surgery are frequently vitamin D deficient before and after surgery. The anatomical changes that occur during some bariatric procedures may lead to decreased absorption of vitamin D, although vitamin D absorption and metabolism has not been quantified or compared across surgeries, and multiple other factors could influence vitamin D status in these individuals. Vitamin D treatment and dosing studies show that there is variability in how individuals respond to supplementation regimens regardless of the bariatric procedure. It is unknown if improving vitamin D status before and/or after bariatric surgery can affect health-related outcomes in this population beyond the traditional roles of vitamin D. Vitamin D has been purported to positively influence a variety of obesity-related comorbidities. Furthermore, in light of the potential role of vitamin D in immunity and inflammation, it seems important to consider the ramifications of vitamin D deficiency in the postbariatric individual in the critical care setting and particularly in the context of aging. Additional research is needed to develop evidence-based guidelines for optimal treatment of vitamin D deficiency in individuals before and after bariatric surgery and to determine the impact of vitamin D repletion on non-bone health-related outcomes in these individuals.