Gastric bypass

Patient profiling for successful weight loss after gastric bypass surgery – intervention in severely obese adults (GO Bypass)

This work package addresses the multiple factors potentially determining the large variation of weight loss after bariatric surgery in severely obesity. It combines surgical, physiological, metabolic, genetic, anthropological, psychological and novel imaging approaches in a genuinely interdisciplinary design.


The aim is to study the multiple factors determining the variation of weight loss after gastric bypass (Roux-en-Y Gastric Bypass surgery or sleeve gastrectomy). The specific aims are to evaluate a) what explains the large individual differences in weight loss seen after gastric bypass surgery, b) if it is possible, pre-operatively, to identify which patients will not obtain sufficient beneficial effects of bariatric surgery in relation to weight loss and quality of life and c) if patients in need of improved care can be identified pre- and/or early post-operatively.


Surgical treatment of severe obesity has consistently been shown to produce superior sustained weight loss and health benefits compared to all other weight loss strategies in severe adult obesity (Sjostrom et al. 2007, Sjostrom et al. 2012, Adams et al. 2012).

However, despite substantial research efforts, the mechanisms postulated to be involved do not fully explain the large weight loss generally seen, and especially not the substantial individual variation in weight loss following the surgical intervention. The fact that some patients are less successful in losing weight is a medical, economical and ethical problem.

So far, no pre-operative indicators of successful weight loss have been identified. Moreover, evidence- based post-operative interventions to support weight loss are limited, and post-operative care usually only targets nutritional deficiencies (Heber et al. 2010).

Thus, there is a need for pre-operative screening tools to predict which patients are at increased risk of not achieving sufficient weight loss, at least not without additional attention/support in addition to their surgical treatment.

In previous studies, weight loss after gastric bypass has not been associated with sustained malabsorption (Odstrcil et al. 2010) of energy or any major alterations in energy expenditure (Tamboli et al. 2010), but with reduced energy intake related to favorable changes in appetite (Bueter et al. 2009). These observations have, to a large extent, been ascribed to alterations in release of appetite-regulating gut hormones (le Roux et al. 2007, Jacobsen et al. 2012).

Moreover, evidence suggests that gastric bypass may affect the hedonic regulation of food intake by altering food preferences leading to more favourable food choices (Miras et al. 2010, Miras et al. 2012).

Furthermore, if the surgical intervention affects post-operative physical activity levels, and how this may affect long-term outcome has been examined in great detail. Socio-cultural and psycho-social factors affect dietary intake as well as eating behavior and physical activity patterns, wherefore these factors may also predict the outcome of surgery (Bocchieri et al. 2002, de Zwaan et al. 2010, Sarwer et al. 2011, Shin et al. 2011, Roberto et al. 2012). Also, genetics add to the individual variation in weight loss after gastric bypass (Still et al. 2011).

Thus, all of these factors are likely to influence weight loss after RYGB. Separately, none of them are likely to explain the variation in weight loss, and it is thus relevant to adopt an interdisciplinary approach to understand the interplay between physiological, genetic and psycho-social factors.

In the Food, Fitness & Pharma UNIK initiative, we adopted a collaborative approach within gastric bypass research, and moved beyond single disciplinary investigations. Preliminary data obtained from this collaboration point towards a combined influence of emotional eating, altered food preferences and appetite-regulating gut hormones on weight loss after gastric bypass.


Social scientific, psychological, behavioral, sensory and physiological methodologies are applied in studies of gastric bypass patients allocated by the gastric bypass team at Køge Hospital, Denmark.

Methodology includes determination of:

  • Anthropometric characteristics including body composition
  • Demographic and socio-economic background of patients, weight biographies of patient and family members, household economy and time-resources will be assessed through structured questionnaires.
  • Physical activity and energy cost of physical activity.
  • Homeostatic appetite regulation in the fasting state and following a standard meal test.
  • Hedonic appetite regulation during meal tests and through in-depth interviews and computerized tests for assessment of reward values of foods. In a subsample of subjects, we also assess changes in BOLD-response to visual food stimuli in the fasted as well as fed state.
  • Changes in food preferences and taste using computerized tests, sensory tests and qualitative interviews.
  • Changes in gut microbiota.
  • General as well as eating psychopathology through standardized psychometric testing. Additionally, impulsivity, self-efficacy and weight bias internalization is assessed along with food addiction and quality of life parameters through standardized questionnaires.
  • Furthermore, social support, food-related knowledge and competence, everyday routines and daily schedules, social obligations and relations as well as habits regarding food, eating and physical exercise, are mapped through individual qualitative in-depth interviews and observations.

A Genetic Risk Score that predicts weight loss after gastric bypass surgery will be assessed utilizing additional samples from the Food, Fitness and Pharma biobank, which comprises more than 500 patients, who have undergone gastric bypass surgery and subsequently been followed for up to 3 years.

Visions for societal impact

  • To construct ‘patient profiles’ integrating physiological, behavioral, genetic, psychological and socio-cultural measures to predict weight changes and challenges following gastric bypass.
  • To improve indication and “contraindication” for bariatric surgery as well as post-operative management and supportive interventions.