Overview

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.

Eligibility

Inclusion Criteria (Healthy Volunteers):

• Age: 30 to 50 years at time of consent
• BMI: 20-25 kg.m-2
• Male or Female
• All races and ethnic backgrounds
• Ability to speak and read English
• Subject has provided informed consent in a manner approved by the IRB and is willing and able to comply with the trial procedures.

Inclusion Criteria (Bariatric Surgery Patients):

• Age: 18 to 65 years at time of consent
• BMI: 35-50 kg.m-2
• Scheduled to undergo bariatric surgery at UTMB
• All races and ethnic backgrounds
• Ability to speak and read English
• Subject has provided informed consent in a manner approved by the IRB and is willing and able to comply with the trial procedures.

Additional inclusion criteria for patients undergoing enhanced metabolic assessment:

• Age: restricted to 30 to 50 years of age
• Undergoing gastric bypass surgery

Exclusion Criteria (Healthy Volunteers):

• 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.)
• Diabetes mellitus or other untreated endocrine or metabolic disorder
• Recent (5 years or less) history of cancer
• Systemic steroids, anabolic steroids, growth hormone, or immunosuppressant use within 6 months.
• Recent (6 months) adherence to a weight-loss or weight-gain diet, resulting in a weight change of 10% or more.
• Body mass index \> 25.5 kg.m-2
• Body mass index \< 19.5 kg.m-2 or recent history (\< 12 months) of disordered eating.
• Acute infectious disease or chronic infection.
• Pregnancy or breast-feeding.
• Recent (1 month) consumption of protein-based sports supplements.
• Any medical condition that, in the opinion of the investigator, would place the subject at increased risk for participation.
• Known allergic reaction to any agent under investigation or required by the protocol, including Phenylketonuria.
• Unable to lie still in a supine position for 10 minutes.
• History of prior non-compliance or the presence or history of a psychiatric condition (including drug or alcohol addiction) that would, in the opinion of the investigator, make it difficult for the subject to comply with the study procedures or follow the investigators instructions.
• Concurrent participation in another research study.
• Use of an investigational agent in the 30 days prior to signing informed consent.

Exclusion Criteria (Bariatric Surgery Patients):

• Fails the medical criteria for bariatric surgery.
• Anemia (hematocrit \< 33 % or donated blood in the past 12 weeks.)
• Recent (5 years or less) history of cancer
• Systemic steroids, anabolic steroids, growth hormone, or immunosuppressant use within 6 months.
• Body mass index \< 35 or \> 50 kg.m-2.
• Acute infectious disease or chronic infection.
• Pregnancy or breast-feeding.
• Any medical condition that, in the opinion of the investigator, would place the subject at increased risk for participation.
• History of prior non-compliance that would, in the opinion of the investigator, make it difficult for the subject to comply with the study procedures or follow the investigator's instructions.
• Concurrent participation in another research study.
• Use of an investigational agent in the 30 days prior to signing informed consent.

Additional exclusion criteria for patients undergoing enhanced metabolic assessment:

• Known allergic reaction to any agent under investigation or required by the protocol, including Phenylketonuria.
• Unable to lie still in a supine position for 10 minutes.
• Previous bariatric surgery or undergoing a procedure other than gastric bypass (e.g. sleeve gastrectomy).