Weight loss surgery is very good at reducing body weight but it can also cause the loss of both muscle and strength. Some patients undergoing weight loss surgery do not achieve their weight loss goals and regain the weight they lost. When this occurs, the loss of muscle and strength combined with the regain of weight can impact the individual's quality of life and ability to remain active and mobile.
The purpose of this study is to understand the behavioral, biological, and genetic factors that influence the success of weight loss surgery and its impact on muscle mass.
Bariatric surgery patients participating in the trial will be monitored prior to, and for a year following weight loss surgery, with data collected about their eating habits, hand grip strength, and the loss of fat, muscle, and body weight following surgery. Some patients will be additionally invited to undergo detailed metabolic assessment, where we will measure how their body uses nutrients it consumes, the composition of their body (e.g. how much lean and fat tissue they have and where it is stored), identify the bacteria living in their gut, and determine their physical performance. In all patients a small sample of gut tissue will be collected at a routine endoscopy performed in advance of weight loss surgery to identify the expression (activity) of genes in their DNA.
Healthy subjects will also be recruited to allow us to compare between healthy weight individuals and those undergoing weight loss surgery. On a single occasion, the healthy volunteers will undergo the same detailed metabolic assessment performed in patients as described above. We will not examine the bacteria living in the gut of the healthy volunteers, nor will we collect gut tissue from these individuals.
Age: 30 to 50 years at time of consent
BMI: 20-25 kg.m-2
Male or Female
All races and ethnic backgrounds
Heart, vascular, or pulmonary disease
Uncontrolled blood pressure (systolic BP > 170, diastolic BP > 95 mmHg)
Impaired renal function (creatinine > 1.5 mg/dl)
Anemia (hematocrit < 33 % or donated blood in the past 12 weeks.)
Patients will be recruited from those electing to undergo bariatric surgery at the University of Texas Medical Branch. Healthy volunteers will be recruited from individuals responding to adverts targeting the Houston - Galveston region.
Cohort
Prospective
Not listed
Whole-body Protein Turnover Rates
Whole-body protein turnover rates measured over a 48 hour period, accomplished via the consumption of a drink containing isotopically labelled (15N) alanine and the subsequent collection of urine for two days. Will be performed on a single occasion in healthy volunteers and up to three times in bariatric patients undergoing metabolic assessment.
Association between foregut gene expression and degree of weight reduction
Assessed only in patients. Gene expression of the foregut will be analyzed in tissue collected from patients during the routine pre-operative upper endoscopy. Subsequently, participants will be stratified into those achieving: \<10%, 10-20%, or \>20% weight loss 12 months post-surgery, and differentially expressed genes between the three groups determined.
Dietary Protein Intake
Dietary protein intake will be determined by participants completing three-day food diaries. This will be performed on a single occasion in healthy volunteers and up to three occasions in bariatric patients undergoing metabolic assessment.
Body weight
Body weight will be determined using digital scales (in kg). Procedures will be performed on a single occasion in healthy volunteers and up to three times in bariatric patients.
Body composition
Body composition will be determined in patients by whole-body bioelectrical impedance. Regional body composition will be additionally assessed in healthy volunteers and bariatric surgery patients undergoing metabolic assessment via whole-body dual-energy x-ray absorptiometry (DXA) imaging. Procedures will be performed on a single occasion in healthy volunteers and up to three times in bariatric patients undergoing metabolic assessment.
Short Physical Performance Battery Test
Assessed using the established short physical performance battery (SPPB) test. Will be performed on a single occasion in healthy volunteers and up to three times in bariatric patients undergoing metabolic assessment.
Changes in the Gut Microbiome post-bariatric surgery
(Measured in patients undergoing metabolic assessment only). The gut microbiome will be analyzed in fecal samples collected from patients, with the type and number of bacteria colonizing the gut determined using established RNA sequencing approaches. Significant changes in the colonizing bacteria in response to surgery will be determined via the collection of samples before surgery (baseline) and two further occasions over a 1 year period following bariatric surgery.
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