The aim of this clinical trial is to investigate the effectiveness of collagen, considered a new approach to prevent muscle mass loss after bariatric surgery, and to demonstrate the relationship between this effect and exercise. The key questions it aims to answer are:

Does whey protein supplementation with collagen combined with resistance exercise prevent muscle mass loss after bariatric surgery? Do whey protein supplementation with collagen combined with resistance exercise affect fat mass after bariatric surgery?

Researchers will compare collagen with whey protein.

The study groups and interventions to be implemented are summarized below:

Group 1: Control Group (CG; n: 10) Whey protein supplementation will be administered Vitamin and mineral supplementation will be administered No resistance exercise will be performed The participants will eat according to bariatric surgery nutrition guidelines and perform physical activities.

Group 2: Whey Protein + Collagen + Exercise Group (WPCEG; n: 10) Whey protein supplements with collagen will be given. Vitamin and mineral supplements will be given. Resistance exercise will be performed. They will eat according to bariatric surgery nutrition guidelines and perform physical activities.

They will begin a resistance exercise program 4 weeks after surgery.

Group 3: Whey Protein + Collagen + No Exercise Group (WPCG; n: 10) Whey protein supplements with collagen will be given. Vitamin and mineral supplements will be given. No resistance exercise will be performed. They will eat according to bariatric surgery nutrition guidelines and perform physical activities.

Group 4: Whey Protein + Exercise Group (WPEG; n: 10) Whey protein supplements will be given. Vitamin and mineral supplements will be given. Resistance exercise will be performed. They will eat according to bariatric surgery nutrition guidelines and perform physical activities.

A resistance exercise program will begin at 4 weeks post-operatively.

Bariatric surgery is an effective method for treating obesity, but a significant decrease in skeletal muscle mass can be observed in the early postoperative period. This loss of muscle mass can negatively affect physical functions, reduce metabolic rate, and make long-term weight maintenance more difficult. Therefore, developing strategies to prevent muscle loss after bariatric surgery is of great clinical importance.

The use of whey protein to support muscle protein synthesis in the postoperative period is a common practice. In recent years, there has been increased scientific interest in the potential of collagen peptides, especially when used in conjunction with resistance exercise, to contribute to muscle mass preservation. However, studies evaluating the combined effect of collagen supplementation and exercise programs in addition to whey protein in individuals undergoing bariatric surgery are limited.

This clinical study aims to investigate the effectiveness of adding collagen to standard whey protein supplementation and a resistance exercise program in preventing muscle loss. Four different groups will be designed to evaluate the independent and combined effects of collagen and exercise:

1. Group receiving only whey protein,
2. Whey + collagen + exercise group,
3. Whey + collagen but no exercise group,
4. Whey + exercise but no collagen group.

All participants will follow a standard post-bariatric surgery nutrition protocol and receive routine vitamin and mineral supplements. The resistance exercise program will begin four weeks after surgery; it will consist of progressively more intense, supervised exercises targeting large muscle groups. Body composition assessments will be performed at baseline and at specified follow-up weeks. The primary outcome measure is change in skeletal muscle mass; secondary outcome measures are fat mass, functional capacity, and exercise compliance.

This study is expected to contribute to the identification of optimal nutrition and exercise strategies to reduce muscle loss after bariatric surgery.

Inclusion Criteria:

• Being between 20-50 years old
• Body mass index; 35 ≤ BMI< 60 kg/m2
• Not being pregnant
• Not being addicted to alcohol and drugs
• Not having entered menopause
• No exercise restrictions

Exclusion Criteria:

• Having at least one of the following inflammatory bowel diseases, upper gastrointestinal bleeding, advanced psychiatric diseases, cancer, and kidney failure.
• using statins
• be pregnant
• Being addicted to alcohol and drugs
• to have entered menopause
• Having exercise restrictions
• Becoming a professional athlete
• Having done more than 60 minutes of regular and structured exercise per week in the last year

man and woman

Individual participant data will not be shared because this study involves identifiable clinical and nutritional data collected at a single center, and participant privacy cannot be fully ensured despite anonymization