Determinants of weight loss after bariatric surgery

Rationale: Obesity is a major public health issue and is associated with several medical conditions including diabetes type 2, cardiovascular disease and cancer. Excess body weight also leads to variable levels of cardiovascular, pulmonary and skeletal muscle dysfunction resulting in poor cardiorespiratory fitness. The complexity of the multicausal nature of obesity makes treatment of this chronic disease difficult. Surgery has proven to be the most effective treatment for morbid obesity. However, weight loss results vary greatly between patients and it is unclear which variables explain the differences between patients with the highest and with the lowest weight loss after surgery. This study is part of the international (European), multicentre study: SOPHIA.
Objective: The overall objective of SOPHIA is to optimize treatment outcome of obesity. We will assess phenotypic, genotypic and behavioural predictors of weight loss after bariatric surgery. In addition, we will compare changes in cardiorespiratory fitness, fat free mass (FFM) and metabolic status and evaluate the relationships of cardiorespiratory fitness and muscle function with weight loss and metabolic health.
Study design: The SOPHIA project is an international (European), multicentre project. The current study is part of a cross-sectional study.
Study population: For this study, we will include patients who underwent primary bariatric surgery and have a minimal follow-up of 18 months. Blood samples will be drawn during the scheduled annual medical check after bariatric surgery. In addition to the standardized items that are part of the annual check-up, blood will be drawn for GWAS analyses. A total of 1000 patients will be included .
Main study parameters/endpoints: The main study endpoint is a prediction model including metabolic, anthropometric, genetic and behavioural characteristics to predict post bariatric surgery weight loss.
Secondary study endpoints are the difference in cardiorespiratory fitness and FFM and the relationship of these measurements with weight loss and metabolic health after bariatric surgery.
Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Patients will be invited to visit the clinic for measurements and drawing of blood during their scheduled annual medical post-bariatric surgery visit. Patients will have an additional of 15mL of blood drawn for GWAS analyses. Since the study measurements are combined with normal follow-up, no extra risk or burden is expected except for a longer duration of the visit.

This study is part of the international, multicentre research project: SOPHIA (Stratification of Obese Phenotypes to Optimize Future Obesity Therapy). The objective of SOPHIA is to optimize treatment outcome of obesity by identifying subpopulations of persons living with obesity in terms of the response to treatment of obesity and the risk of complications of obesity itself. To achieve this, the first step is to create an international database on treatment outcomes in patients with obesity. This database will include patients undergoing different types of treatment for obesity. Our cohort will only include patients who have undergone bariatric surgery.

At a scheduled appointment anthropometric measurements will be completed by the researcher. As well, blood samples will be drawn for annual medical health checks, which is a standard part of the regular postoperative follow-up at NOK. There will be one extra blood sample for the GWAS analyses. In addition data will be collected from the electronic patient record . This data will be collected up to the moment that the patient is included in the study, for example, if a patients is included at 4 years follow-up, all data including the 4 year follow-up data will be used for study purposes