The goal of this clinical trial is to compare the effects of resistance exercise and endurance in post-bariatric surgery patients with insuficcient weight loss. The main question it aims to answer is:

• Is resistance exercise more effective than endurance exercise in preventing obesity relapse in post-bariatric surgery patients with insuficcient weight loss?
• Is resistance exercise more effective than endurance exercise in increasing resting metabolic rate in post-bariatric surgery patients with insuficcient weight loss?

Participants will be randomly assigned to one of the following groups:

• Resistance group: performing resistance exercise-training for 16 weeks
• Endurace group: performing endurance exercise-training for 16 weeks
• Control group: no intervention / standard medical care

As lean body mass losses following bariatric surgery (BS) negatively affect resting metabolic rate (RMR), metabolic regulation and physical function, the researchers hypothesize that resistance exercise (REx) could more effectively prevent obesity relapse following BS. Also, the increased mechanical loading on lumbar spine intervertebral discs is associated with an ampered spinal health and low pressure pain threshold sensitvity in these patients. The main purpose of this project is to determine which exercise mode is best suited to prevent obesity and increase RMR of post-BS patients with insufficient weight loss.

To accomplish this, the researchers will perform a single center 3-parallel-arm open-label randomized clinical trial to determine if resistance exercise is superior to endurance exercise in reducing obesity relapse in post-BS patients with insufficient weight loss.

Aditionally we aim to investigate if resistance exercise is more effective than endurance exercise in producing changes in pressure pain threshold, spine mobility and thoracolumbar strength in post-BS patients with insufficient weight loss.

Patients will be enrolled in 4 (possibly 5) consecutive cohorts of n=20. These must be between 18 and 65 years old and have performed bariatric surgery in the prior 18 to 24 months. Participants will be randomly assigned one of three groups: control (CON), resistance exercise (REx) and endurance exercise (EEx), while the latter two will be enrolling exercise-training programs. All the groups will be assessed in two moments: baseline and 16 weeks (end of exercise programme). Both the training sessions and the assessments will be performed at Porto Faculty of Sports (FADEUP).

The study is expected to run for 2.5 years while including 5 cohorts of patients.

Participants will be the chance to participate for free in exercise sessions (REx, EEx ) and to have free access to the results of health evaluations performed. Main risks for participants in the study will be the potential adverse events associated with exercise or physical evaluations and the burden of time spent in exercise sessions and evaluations.

Inclusion Criteria:

• Age between 18 and 65 years (until the end of intervention)
• Having performed primary bariatric surgery (gastric sleeve or RYGB methods) in the prior 18 to 24 months in S. João Hospital center.
• Willing to participate and commit to intervention

Exclusion Criteria:

• Already taking part in a structured exercise programme.
• Presenting health condition contraindicating exercise practice
• Inability to commit with intervention