Physical Activity Following Surgery Induced Weight Loss
Condition: Obesity
MeSH terms: Weight Loss
Study type: Interventional

Summary: 
      The primary objective of this study will be to determine the effects of physical activity in
      patients during substantial surgery-induced weight loss.

      A randomized controlled physical activity intervention trial in a group of patients
      undergoing bariatric surgery for weight loss. The study will involve two sites with an active
      bariatric surgery program, which have a strong track record of bariatric surgery research.
      The study will include 160-200 subjects. Changes in the primary outcome variables will be
      determined in previous gastric bypass patients as a result of 6 months of moderate physical
      activity compared to an educational control group not engaged structured exercise.
    

Detailed description: 
      The primary objective of this study will be to determine the effects of physical activity in
      patients during substantial surgery-induced weight loss. We propose to employ a randomized
      controlled physical activity intervention trial in a group of patients undergoing bariatric
      surgery for weight loss. The study will involve two sites with an active bariatric surgery
      program, which have a strong track record of bariatric surgery research.

      Recruitment goals are 160-200 gastric bypass patients who will undergo 6 months of moderate
      physical activity compared to an educational control group not engaged structured exercise.
      Subjects will be included if their BMI is less than 55 kg/m2 prior to surgery and they are
      located relatively close to centers for intervention sessions. At baseline (3 months
      following surgery) and 6 months later (9 months following surgery), subjects will have a CT
      scan, IV glucose tolerance test (IVGTT) and muscle biopsy (~8 hour visit). They will be
      scheduled for separate visits for a test of physical fitness (VO2max) and general body
      composition (DXA scan)(~2 hour visit), and a 15-min sub-maximal exercise session.

        1. Physical activity group: Subjects will be progressed to 4-5 days per week, 30-45 min per
           session (120-180 min per week) of moderate intensity exercise.

        2. Control (educational) group: Subjects will receive their usual care following surgery
           that includes information on physical activity. They will also be asked to participate
           in monthly health education sessions.

      We will promote this study as one that will help determine whether physical activity may be
      beneficial in addition to their weight loss.

      Aim 1: Insulin resistance and metabolic risk factors. Approach: To address Aim 1, we will
      determine 6-month changes in insulin sensitivity in subjects after 3-month initial weight
      loss from bariatric surgery. As outlined above, we will employ a randomized controlled
      physical activity intervention trial in which half of the subjects will be entered into a
      physical activity group, while the other half will participate in monthly health education
      sessions (control). By randomizing these groups three months after initial weight loss, both
      groups should begin the intervention with similar baseline characteristics (e.g. insulin
      sensitivity, body weight, physical fitness, etc.). We are not attempting to determine the
      effect of the weight loss per se on insulin sensitivity. However, we realize that the amount
      of weight loss could potentially have a major confounding influence on detecting changes in
      insulin sensitivity between the two groups. Thus, we will examine the degree of weight loss
      as a covariate in our analyses.

      Aim 2: Intramyocellular lipids and body composition. Approach: We will examine pre to post
      intervention, changes in intramyocellular lipid determined with percutaneous biopsies, as
      well as abdominal and intermuscular adipose tissue determined by CT imaging.

      Aim 3: Mitochondria content, function and fat oxidation. Approach: We will use three
      complimentary measures to quantify changes in oxidative metabolism before and after the
      randomized controlled trial described above. All three of these measures will make specific
      contributions to this specific aim. Rates of resting post-absorptive fat oxidation will be
      measured with indirect calorimetry. Since skeletal muscle accounts for the vast majority of
      energy production during physical activity, sub-maximal exercise is a good model to assess
      skeletal muscle fatty acid metabolism. We will employ whole body gas exchange indirect
      calorimetry during moderate exercise designed to elicit high rates of fatty acid oxidation.
      The non-invasive measures of systemic fat oxidation during both resting and exercise
      conditions procedures take very little time and present relatively little burden on the
      volunteers or technical staff, thus providing an efficient means to obtain significant
      information concerning the capacity for fat oxidation in vivo. Muscle biopsy samples will be
      obtained before and after the trial to measure changes in the oxidative capacity (electron
      transport chain activity, in vitro fatty acid oxidation, muscle fiber type and oxidative
      enzyme (succinate dehydrogenase) staining activity of muscle.
    

Intervention name(s): Physical Activity
Intervention type(s): Behavioral
Intervention description(s): 1. Physical activity group: Subjects will be progressed to 4-5 days per week, 30-45 min per session (120-180 min per week) of moderate intensity exercise. 2. Control (educational) group: Subjects will receive their usual care following surgery that in addition to their weight loss.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: Body fat; Exercise; Fatty acids; Impaired glucose tolerance; Insulin resistance; Insulin Sensitivity; Metabolic syndrome; Obesity; Physical activity; Weight Loss