This study aims to determine how different types of exercise regimens (resistance, aerobic, or combined exercise regimens) can be used to minimize muscle loss and mobilize body fat in severely obese patients after bariatric surgery (BS), despite the rapid surgery-induced weight loss. Additionally, the study will examine how changes in the intestinal microbiota following BS act as a mediation factor that alter tissue-specific responses in muscle and adipose tissue. The study will also evaluate the effect of different types of exercise regimens on cardiometabolic markers, endocrine response, and physical function following BS.

Sixty sedentary (regular exercise <1 hour per week) candidates to bariatric surgery at Herzliya Medical Center will be recruited to participate in this six-month-long randomized control study. Participants will be randomly assigned to either one of three exercise regimens intervention groups (aerobic, resistance, or a combined exercise regimen combining aerobic and resistance exercises) or a control group that will receive standard care. Training will be supervised and matched for metabolic equivalent (METs). The intervention will take place at the Sylvan Adams Sports Institute at Tel Aviv University and an online platform.

All measurements will be taken at a presurgical baseline assessment and throughout the study, and will include changes of muscle mass and adipose tissue distribution, measured by a 3-Tesla magnetic resonance imaging (MRI); body composition- will be assessed using multichannel bioelectrical impedance (Seca); Bone mass, will be measured by a Dual-energy X-ray absorptiometry (DEXA); microbiota composition and changes will be evaluated by stool samples that will be subjected to 16S ribosomal ribonucleic acid (16s rRNA) profiling and metagenomics analysis; fasting blood samples will be used to examine endocrine control and cardiometabolic markers; anthropometric measurements to assess surgery results associations with physical activity outcomes and physical function will be assessed by several validated performance assessments, including handgrip, six-minute walk, sit-to-stand, maximum voluntary contraction, and maximal oxygen consumption (VO2max).

The primary aim will be to determine how different types of exercise regimens (resistance, aerobic, or combined exercise regimens) can be used to minimize muscle loss and mobilize body fat in severely obese patients after BS, despite the rapid surgery-induced weight loss.

Secondary aims will include: I. To examine the effect of different exercise regimens on the composition and diversity of microbiomes, and their role in mediating muscle mass preservation following BS. II.Evaluate changes in cardiometabolic markers and endocrine response to different exercise regimens and evaluates microbiome mediation of these changes after BS. III.Assess the effect of different exercise regimens on physical function among patients following BS. IV.Clarify the mechanisms of muscle preservation and fat loss involving hormonal response and atrophy related-genes expression.

After baseline measurements (detailed below), participants will be randomized into one of four groups: 1. control group (n=15) that includes routine health care; 2. aerobic exercise training group (n=15), 3. resistance exercise training group (n=15), 4. combined aerobic and resistance exercise training group (n=15). Training sessions will be both in-person and as online exercise supervision. All groups will be supported by a dietitian as part of the routine health care after the bariatric surgery. The dietetic program for all groups will consist of a balanced diet by diet progression guidelines for bariatric patients (XX,ZZ) and the bariatric food pyramid (55). The protein content will be a minimum of 60 gr/protein per day, according to current guidelines (XX,ZZ) . Each training session will increase gradually up to 60 minutes per session, three times a week. Participants will be randomized into 4 groups for 26 weeks of intervention including aerobic, resistance, combined exercise training (aerobic + resistance) and a control group without exercise training.

All exercise training will be matched in metabolic equivalent (METs) and the time of training per week. Participants will begin a two weeks exercise adaptation period at 3-4 postoperative weeks. The activity adaptation plan will consist of 15-20 min. of walking, three times per week, at an intensity of 40-60% of peak oxygen consumption (VO2) or rate of perceived exertion (RPE) 4-6 on the Borg scale for all intervention groups. Following this period, each group will participate in a specific progressive training with the following regimen:

1. Aerobic exercise training group, weeks 5-8 after surgery: this training will consist of 30 min. of walking, 3 times per week at an intensity of 60-70% of peak VO2 or RPE 6-7 on Borg scale.

   Weeks 9-26 after surgery: this training will consist of 60 minutes of exercise, 3 times per week at an intensity of 65-80% of peak VO2 or RPE 6-8 on the Borg scale. The aerobic exercises will consist of a treadmill or outside walking or running, stationary cycling or elliptical trainer in continuous and interval training.

2. Resistance exercise training group, weeks 5-8 after surgery: this training will consist of 5-10 minutes of warmup, followed by 6-8 multi-joint exercises for major muscle groups, comprising 2 sets of 10 to 25 repetitions at 40% of the one-repetition maximum (1-RM) for each exercise. The intensity will increase on weeks 9-26 after surgery to 8-10 multi-joint exercises of 3-4 sets of 10 to 25 repetitions. For this training participants will use free-weights and bodyweight exercises.

3. The combination exercise training will consist of a combined aerobic and resistance exercise training sessions three times weekly. At weeks 5-8 after surgery, the sessions will include 5-10 minutes of warmup, followed by 3-4 multi-joint exercises for major muscle groups, comprising 2 sets of 10 to 25 repetitions at 40% of the one-repetition maximum (1-RM) for each exercise. Afterward, the aerobic part of the training will consist of 10-15 minutes of aerobic exercises (treadmill or outside walking or running, stationary cycling or outdoors or elliptical trainer) at 60-70% of peak VO2 or RPE 6-7 at Borg scale.

   The intensity will increase on weeks 9-26 after surgery to 4-5 multi-joint exercises of 3-4 sets of 10 to 25 repetitions and 30 minutes of aerobic exercises at 65-80% of peak VO2 or RPE 6-8 at Borg scale.

4. The control group will receive conventional treatment so as the other groups (medical and nutritional follow up).

Inclusion Criteria:

• Sedentary participants: regular exercise performed <1 hour per week
• Candidates for primary bariatric surgery at Herzliya Medical Center in accordance to the National Institutes of Health (NIH) criteria for surgery: (body mass index (BMI) > 40 without coexisting co-morbidities or BMI > 35 with > 1 severe obesity-related comorbidities)
• Sex: all
• Age: 18 to 65 years.

Exclusion Criteria:

• Severe cardiopulmonary disease (e.g., recent myocardial infarction or unstable angina)
• Musculoskeletal or neuromuscular impairments that preclude exercise training
• Cognitive impairments
• Use of drugs that affect bone or muscle metabolism (mainly steroids)
• Patients with previous bariatric surgery