How does weight loss (bariatric) surgery change diet and the bacteria in our stomachs (gut microbiota), and how can these changes influence our brain?

Bariatric surgery is the most common treatment for individuals with severe obesity. There is new research showing that bariatric surgery might improve people’s brain health, but unfortunately, we don’t know how or why this is.

This study aims to provide information that could help us better understand the connection between diet, microbiota and brain health (brain functions such as memory, language, concentration, etc.).

For most people, bariatric surgery helps them lose weight and be healthier. They also lead to large changes in how people eat and way the body works.

The bacteria in our stomachs (which is called the gut microbiota) can impact our health, including our brain health. Importantly, bariatric surgery greatly influenced these bacteria and they are also affected by what we eat. This means that by looking at how bariatric surgery changes what we eat, our stomach bacteria, and our brain health we can start to understand how they are all connected.

Our study will follow 120 adults who are having bariatric surgery. We will measure the following things: blood and stool samples; people’s diet (dietary composition and eating patterns); weight (height, weight, waist and hip circumference, body fat composition); and brain structure and function measure both before and after surgery.

We will compare these individuals to 60 adults who are waiting to have the surgery and 60 individuals who are not eligible for bariatric surgery who will do similar measure at similar times, but without the surgery.

The main objective of this project is to:

Explore how dietary patterns and gut microbiota change from 3 months before to 6 months after bariatric surgery and if these changes might be related to improved brain structure and function one year after surgery.

Another goal will be to:

See how surgery changes other things in our body such as, how our body reacts to infections and the hormones that control a number of biological processes, that might explain how these relationships work.

Contact us: embrace.cnmtl@ssss.gouv.qc.ca


Project Team

Principal Investigators:

Simon L. Bacon, PhD (physiologist), Professor, Department of Health, Kinesiology, and Applied Physiology, Concordia University, Co-Director Montreal, Behavioural Medicine Centre (MBMC), Centre intégré universitaire de santé et de services sociaux du Nord-de-l’Île-de-Montréal (CIUSSS) – Hôpital du Sacré-Coeur de Montréal (HSCM) Research Centre

Tair Ben Porat, PhD (nutritionist), Department of Health, Kinesiology, and Applied Physiology, Concordia University and CIUSSS du Nord-de-l’Île-de-Montréal – HSCM Research Centre

Co-Principal Investigator:

Kim Lavoie, PhD (psychologist), Department of Psychology, Université du Québec à Montréal and CIUSSS du Nord-de-l’Île-de-Montréal – HSCM Research Centre


  • Angela Alberga, PhD (physiologist), Department of Health, Kinesiology and Applied Physiology, Concordia University
  • Marie-Claude Audet, PhD (neuroscientist), School of Nutrition Science, University of Ottawa
  • Sylvie Belleville, PhD (neuropsychologist), Institut universitaire de gériatrie de Montréal (IUGM) research director and professor at Univeresité de Montréal
  • Tamara Cohen, PhD (nutritionist), Director of Dietetics at UBC
  • Dajana Vuckovic, PhD (biochemist), Department of Chemistry and Biochemistry, Concordia University
  • Pierre Y. Garneau, MD (surgeon), Chief of general surgery service, CIUSSS du Nord-de-l’Île-de-Montréal – HSCM
  • Patrick Marion (patient investigator)
  • Radu Pescarus, MD (surgeon), CIUSSS du Nord-de-l’Île-de-Montréal – HSCM
  • Elham Rahme, PhD (biostatistician)- Professor at McGill
  • Sylvia Santosa, PhD (nutritionist), Research Centre, CIUSSS du Nord-de-l’Île-de-Montréal – HSCM and Department of Health, Kinesiology and Applied Physiology, Concordia University
  • Anne-Sophie Studer, MD (surgeon), CIUSSS du Nord-de-l’Île-de-Montréal – HSCM

Students and Staff:

  • Reyhaneh Yousefi (PhD candidate), Department of Health, Kinesiology and Applied Physiology, Concordia University
  • Robbie Woods (PhD candidate), Department of Psychology, Concordia University
  • Julie Favron-Godbout, research staff
  • Raphaèle Denis, research staff
  • Marie Peron, research staff


More About the Project Team

Simon Bacon, PhD

Simon Bacon, PhD, FTOS, FCCS, FABMR, is the principal investigator of the Embrace project and Co-Director of the Montréal Behavioural Medicine Centre. He is a researcher at the Centre intégré universitaire de santé et service sociaux du Nord-de-l’Île-de-Montréal, and co-lead of the International Behavioural Trials Network (IBTN). He is a full professor in the Department of Health, Kinesiology, and Applied Physiology at Concordia University, the Canadian Institutes of Health Research (CIHR) Strategy for Patient-Oriented Research (SPOR) Chair in Innovative, Patient-Oriented, Behavioural Clinical Trials, and the FRQS co-Chair in Artificial Intelligence and Digital Health for Health Behaviour Change. Dr. Bacon’s Research is centered around the role of lifestyle factors, including health behaviours and psychological factors, in the development (primary and secondary prevention) and progression (tertiary prevention) of non-communicable chronic diseases (NCDs), and certain communicable diseases (e.g., COVID-19). Dr. Bacon has won research awards from the Canadian Hypertension Society, Canadian Institutes of Health Research, McGill University, National Institutes of Health (US), European Society of Hypertension, and International Society of Psychoneuroendocrinology.

Tair Ben Porat, PhD

Tair Ben Porat, PhD, graduated with Excellence A first degree in Nutritional science at the Agriculture Faculty of the Hebrew University, and obtained her PhD at the Department of nutrition and Metabolism of the Faculty of Medicine the Hebrew University, Jerusalem, Israel. She also holds a Master of Public Health (MPH), from the Sackler School of Medicine, Tel Aviv University. Her research focuses on nutritional and metabolic aspects pre- and post-bariatric surgery. During the last decade, Dr Ben Porat have managed the bariatric surgery nutritional therapy for patients with severe obesity at Hadassah Hebrew University Medical Center. She has previously initiated the establishment of a prospective medical database for bariatric patients in Hadassah Hebrew University Medical Center, and since then, she has been a main/co-investigator and collaborator on a considerable number of studies in fields of obesity and bariatric surgery. Dr Ben Porat currently serves as the Chair of the “Bariatric Surgery Forum” of the Israeli Dietetic Association, as a committee member of the Israeli Society for Metabolic and Bariatric Surgery, and as the Chair of the Integrated Health Committee the European chapter of the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO-EC). Through these, she has been able to translate her work into clinical guidelines and national position statements. In 2020 Dr Ben Porat has been awarded with the Hebrew University Excellent PhD Dissertation and the Hebrew University Scholarship Program for Post-Doctoral Excellent Female Students, as well as the FRQS scholarship (QC, Canada) for a 2-year postdoctoral fellowship. Due 2021 she has joined the Montreal Behavioral Medicine Center for her post-doctoral studies. Her focus is in exploring and understanding bariatric procedure’s impact on mental, nutritional and metabolic outcomes among target groups as well as elucidating the combination of genetic/microbiota factors and patient behavior/lifestyle as a key factor to establish innovative personalized future therapy.

Kim Lavoie, PhD

Kim Lavoie, PhD, FCPA, FABMR is is Co-Director of the Montréal Behavioural Medicine Centre, and a researcher at the Centre intégré universitaire de santé et service sociaux du Nord-de-l’Île-de-Montréal. She is a full professor in the Department of Psychology at the University of Quebec at Montreal (UQAM) and holds the Tier 1 Canada Research Chair in Behavioural Medicine. She holds several national and international leadership positions including Co-Lead of the International Behavioral Trials Network and Chair of the Canadian Network for Health Behavior Change. Dr. Lavoie’s work focuses on research in three areas: 1) the impact of psychological stress (e.g., depression, anxiety) and lifestyle factors (diet, exercise, smoking, medication adherence) on the development and progression of chronic illnesses (e.g., cardiovascular disease, asthma, COPD, and obesity); 2) psychophysiological and behavioral mechanisms linking psychological stress to disease; and 3) behavioural medicine (e.g., behavioral interventions for chronic illnesses, including motivational communication and cognitive-behavioral therapy). The goals of her research program include understanding how psychological and behavioural factors impact chronic disease development and progression, and using this data to develop, test and disseminate evidence-based behavioural interventions that target these factors. She is an internationally recognized expert in motivational communication; over 15,000 health professionals across Canada, the US, Europe, Australia and New Zealand have attended her professional training workshops. She currently holds multiple grants in the area of motivational communication training and efficacy for behaviour change in chronic disease.

Angela Alberga, PhD

Angela Alberga, PhD, is an Assistant Professor in the Department of Health, Kinesiology and Applied Physiology at Concordia University. Her interdisciplinary research program focuses on better understanding how societal, school and other broader institutional factors influence weight-related issues such as obesity, eating disorders, physical inactivity and weight stigma. Her MSc and PhD research focused on examining the effects of aerobic training, resistance training and combined aerobic and resistance training on the cardiometabolic health of adolescents with obesity. Her PhD work resulted in several high impact research articles in the field of medicine and obesity.  To complement her expertise in clinical health research improving the physiological health of youth with obesity, her postdoctoral training focused on better understanding the psychological impacts of obesity. Her postdoctoral work also resulted in several high-impact publications including her co-authorship of the weight bias chapter of the new 2020 Canadian Adult Obesity Clinical Practice Guidelines published in the Canadian Medical Association Journal. Her graduate studies allowed her to collaborate with many multidisciplinary researchers (medicine, psychology, physiology, public health, etc.) to develop her skills in communication and knowledge transfer and improve her abilities as a sensitive communicator about body weight-related issues.

Marie-Claude Audet, PhD

Marie-Claude Audet, PhD, is an Associate Professor in Stress, Nutrition, and Mental Health in the School of Nutrition Sciences at the University of Ottawa. She also holds appointments in the Department of Cellular and Molecular Medicine at the University of Ottawa as well as at the Institute of Mental Health Research of the Royal Ottawa Mental Health Centre and the Department of Neuroscience at Carleton University. Dr. Audet’s current research program aims to understand how stressful experiences across the lifespan may come to alter the gut microbiota-immune-brain axis and promote vulnerability to mental illnesses, particularly depressive and anxiety disorders. A central component of her research involves the development of lifestyle approaches, including dietary and microbiota-targeted interventions and changes in physical activity, to prevent and/or attenuate symptoms of mental illnesses through the modulation of this axis. As the prevalence of depression and anxiety disorders in women is about twice as that of men, all her work is conducted in females and males, to allow the establishment of sex differences in relation to the microbiota, inflammatory and behavioral effects of stressors and of lifestyle interventions. Her research is currently funded by grants from the Natural Sciences and Engineering Research Council of Canada, the Social Sciences and Humanities Research Council (New Frontiers in Research Fund –Exploration), the Weston Family Foundation, as well as several internal awards.

Sylvie Belleville, PhD

Sylvie Belleville, PhD, is a full professor at the Psychology Department of University of Montreal and researcher at the Research Center of the Institut Universitaire de Gériatrie de Montréal. She is recognized for her work in the area of cognitive training for older adults and persons at risk of dementia and on the prevention of age-related cognitive decline. She identified processes of compensation and plasticity in mild cognitive impairment using brain imaging techniques. She also developed an important research program on the neuropsychology of memory in aging and dementia and has contributed to a better understanding of the neuropsychological deficits found in persons with very early signs of Alzheimer’s disease or mild cognitive impairment. She published 242 peer-reviewed articles. She currently holds a Tier 1 Canada Research Chair on the Cognitive Neuroscience of Aging and Brain Plasticity. She leads the Québec Consortium Québécois for early identification of Alzheimer’s disease (CIMA-Q) and the national team “Cognitive Intervention, Cognitive Reserve and Brain Plasticity” and “Brain Health Support Program” for the Canadian Consortium on Neurodegeneration in Aging. She received many prizes in recognition of her work, including the Adrien Pinard Prize of the Quebec Psychology Research Society, Professional Prize of the Quebec Psychologist Association and Doctorat Honoris causa from Mons University, Belgium. She is also a member of the prestigious Canadian Academy of Health Sciences.

Tamara Cohen, PhD

Tamara Cohen, PhD, is a registered dietitian, the Program Director of Dietetics and an Assistant Professor in the Faculty of Land and Food Systems at the University of British Columbia (UBC) (Food, Nutrition and Health | Human Nutrition). She is also an Investigator at the BC Children’s Hospital Research Institute. Dr. Cohen received her PhD in Nutritional Sciences from the School of Nutrition (McGill University, Montreal, QC). Her current research program focuses on eating behaviours throughout the lifespan, with the goal of improving dietary habits. To do so, her team bases their research on theoretical frameworks and applies them to the nutrition / dietary context. Her team is also involved in creating nutrition education tools, including creating a smartphone dietary self-monitoring application, with the goal of educating people about healthy eating and then assessing the tool’s impact on dietary change. Dr. Cohen holds a Scientist in Nutrition and Lifestyle award (2018-2023) with Concordia University through the R. Howard Webster Foundation (PERFORM Centre).

Dajana Vuckovic, PhD

Dajana Vuckovic, PhD, is an Associate Professor and Concordia University Research Chair (Tier 2) in the Department of Chemistry and Biochemistry and the Director of the Centre for Biological Applications of Mass Spectrometry at Concordia University. Dajana completed an Honorary BSc in chemistry from the University of Toronto, a PhD in analytical chemistry focusing on in vivo metabolomics at the University of Waterloo, and postdoctoral studies in chemical and quantitative proteomics at the University of Toronto. Beyond her research in clinical metabolomics and lipidomics which focuses on the development of novel methods to measure unstable and low abundance metabolites, Dajana is an active member of the Metabolomics QA & QC Consortium (mQACC) which aims to develop and disseminate new community-based guidelines to ensure high quality of untargeted metabolomics studies.

Pierre Y. Garneau, MD

Dr. Pierre Y. Garneau completed his medical and surgical training at Laval University. After a year of subspecialization at the University of Montreal, he began his career at the Hôpital du Sacré-Coeur in 1997 and performed the first bariatric procedure there. He then gradually devoted his career to bariatric, laparoscopic and robotic surgery. He is currently the director of the university training program in bariatric surgery at the University of Montreal. He is the Head of the Department of Surgery at CIUSSS-NIM and is also the Secretary of the Canadian Association of Bariatric Physicians and Surgeons (CABPS). His main research interests are focused on revision surgery.

Patrick Marion, BBA

Patrick Marion is an entrepreneur and a businessman. He has a Bachelor’s degree in Business Administration from the Université du Québec à Montréal. Patrick underwent bariatric surgery in August 2016. His engagement as an executive member of the Patient-Researcher Committee at the CIUSSS du Nord-de-l’Île-de-Montréal – Hôpital du Sacré-Cœur de Montréal has been a natural fit. Patrick is eager to improve the experience and quality of care for people living with obesity and those undergoing bariatric surgery.

Radu Pescarus, MD

Dr. Radu Pescarus completed his five-year residency in General Surgery at the University of Montreal. He then continued his subspecialty in Canada with a one-year fellowship in Bariatric and Minimally Invasive Surgery at McMaster University. Subsequently, he underwent a second fellowship in Portland, USA to further his knowledge in oesophageal gastric surgery as well as in the new field of gastrointestinal therapeutic endoscopy. He takes part in the surgery department of the Hôpital du Sacré-Coeur de Montréal and is currently an Associate Professor at the University of Montreal. His three areas of expertise are minimally invasive bariatric surgery, diaphragmatic and gastric surgery, as well as gastrointestinal therapeutic endoscopy. Dr. Pescarus is currently the Co-chair of Research in the General Surgery Program at the University of Montreal and as such is involved in research development throughout the residency program. His personal research interests include clinical and evaluative research in revisional bariatric surgery and the endoscopic treatment of upper gastrointestinal surgical complications.

Elham Rahme, PhD

Elham Rahme, PhD, is an associated professor at the Division of Clinical Epidemiology of the Department of Medicine at McGill University. She has over 25 years of experience in epidemiology, pharmacoepidemiology and biostatistics research. Amongst all the articles she has published and abstracts she has presented at national and international meetings, she has used the Quebec health administrative databases and survey data to conduct large population-based studies in several areas of research including mental health, autoimmune diseases, and cardio-metabolic diseases. Using these data, she has quantified the dual relationship between depression and diabetes and demonstrated, among other things, a higher risk of diabetes in individuals with severe (versus mild) psoriasis and a higher risk of depression in young adults with diabetes.

Sylvia Santosa, PhD

Sylvia Santosa, PhD, RD (CDO) is an Associate Professor in the department of Health, Kinesiology, and Applied Physiology at Concordia University, and a Canada Research Chair, Tier 2 in Clinical Nutrition. She earned her PhD in Nutritional Sciences from McGill University and is a registered dietitian in the College of Dietitians of Ontario. Her multidisciplinary lab, the Metabolism, Obesity, and Nutrition (MON) Lab at the PERFORM Centre, combines unique biological, physiological and nutritional techniques to investigate and understand the underlying effects of obesity that contribute to weight gain and disease. Her research has two main streams: the clinical stream investigates the nutritional needs of bariatric surgery patients, and the metabolic stream examines factors affecting regional fat tissue characteristics and how these characteristics, in turn, contribute to disease risk. The main goals of her research are to determine what makes obesity pathology different between individuals and how these differences can be accounted for in designing the better treatments for obesity.

Anne-Sophie Studer, MD

Dr Anne-Sophie Studer completed her medical degree in France through the University of Aix-Marseille. During her surgical training in general and digestive surgery, she also completed a master’s degree in biological anthropology. Upon completion of resident training, Dr Studer undertook multiple fellowships in both France and Canada, in minimally invasive surgery, bariatric surgery and trauma/acute care. Dr Studer is currently a practicing attending surgeon at Hospital Du Sacre-Coeur, Montreal, a tertiary teaching hospital affiliated with the University of Montreal. She has a special interest in revisional bariatric surgery and performs complex revisions with both laparoscopic and robotic platforms. Dr Studer also participates in the on call general surgical roster, performing emergency general surgery and trauma procedures.

The EMBRACE Project is funded by the Weston Family Foundation through its Microbiome Initiative. The Weston Family Foundation invests in innovation and learning to deliver measurable impacts to the well-being of Canadians.

Institutional Partners

This Montréal Behavioural Medicine Centre (MBMC) project is led in partnership with the Centre intégré universitaire de santé et de services sociaux du Nord-de-l’Île-de-Montréal (CIUSSS-NIM), Concordia University, the University of Ottawa, and the Institut universitaire de gériatrie de Montréal (IUGM).