Photographic Food Recognition and Meal Size Estimation Before and After Roux-en-Y Gastric Bypass
Condition: Obesity, Morbid; Bariatric Surgery; Roux-en-Y Gastric Bypass; Food Preferences
MeSH terms: Obesity, Morbid
Study type: Observational

Summary: 
      Direct measurements of changes in food selection in humans after RYGB have been limited by
      the unreliability of patients, which poses significant methodological and conceptual
      challenges to researchers and study design. Self-monitoring requires time and effort, and
      many find tracking of dietary intake tedious, which contributes to attrition. Direct
      measurements, however, represent an essential component in the attempt to understand how RYGB
      alters eating and food preferences, but laboratory settings preclude a real-life environment.

      The aim of this study is to investigate changes in food preferences, total energy intake of
      the three primary macronutrients and meal patterns between obese women (BMI ≥ 35) before and
      after Roux-en-Y gastric bypass and lean (BMI ≤ 25) and obese (BMI ≥ 35) controls by means of
      photographic food recognition with a mobile application.
    

Detailed description: 
      Introduction

      Obesity is one of the most important public health conditions worldwide. The morbidity can
      largely reduce life expectancy. Bariatric surgery for severe obesity is an effective
      treatment that results in the improvement and remission of many obesity-related
      comorbidities, cardiovascular benefits, as well as sustained weight loss and improvement in
      quality of life. Different surgical procedures for weight loss have been developed, with the
      most common ones being sleeve gastrectomy (SG) and Roux-en-Y Gastric Bypass (RYGB). RYGB is
      the most commonly used procedure for weight loss in Switzerland, even though in the last
      decades there has been a global shift towards SG. Independently from the applied procedure,
      bariatric surgery remains the most effective and durable intervention for obesity. Modern
      bariatric surgery has an excellent safety profile, even though complications in the short and
      long term have been reported. Extensive research also increased the understanding of the wide
      range of mechanisms underlying the effectiveness of bariatric surgery. The relative
      contributions of these mechanisms vary according to the chosen procedure, where altered
      satiety and hunger are considered important factors after RYGB. Other mechanisms have also
      been proposed, including changes in gut hormones, reduced appetite, increased satiation,
      increased energy expenditure, alteration in the gut microbiota and bile acids levels and
      composition, as well as changes in vagal nerve signalling. Changes in food preferences have
      also been implicated as an important candidate mechanism as patients prefer low-sugar low-fat
      food and report finding food, in general, less enjoyable after RYGB. Both humans and rats eat
      less and display altered food preferences after RYGB, but the underlying behavioural
      mechanism remains unclear.

      The aim of public health policy in the treatment of obesity should be the development of
      effective prevention and better therapies which would eliminate the need for surgery
      altogether. Until then, bariatric surgery is safe, effective, affordable, and with large room
      for improvement. Furthermore, a deeper understanding of the physiological changes underlying
      the improvement of the morbidity may help in developing new therapies. So far, direct
      measurements of changes in food selection in humans after RYGB have been limited by the
      unreliability of patients, which poses significant methodological and conceptual challenges
      to researchers and study design . Self-monitoring requires time and effort, and many find
      tracking of dietary intake tedious, which contributes to attrition . Direct measurements,
      however, represent an essential component in the attempt to understand how RYGB alters eating
      and food preferences, but laboratory settings preclude a real-life environment. Consequently,
      obesity researchers have attempted to develop new easier tracking methods such as photography
      of food items to monitor dietary intake both in the clinical setting and everyday life. These
      new methods seem more effective compared to others. For instance, mobile phone applications
      of photographic food recognition (PFR) such as SNAQ enable patients to record and submit
      consumed food items, portion sizes and frequency of consumption during a pre-defined period.
      However, this technology is still in its infancy and assessment procedures need to be
      validated by trained professionals. The doubly labeled water (DLW) method has been proposed
      as a gold standard to assess free-living total energy expenditure and can be used to monitor
      the body composition (BC) and total energy expenditure (TEE) of an individual under
      circumstances of energy balance based on dilution equations of the labelled isotopic elements
      in the body . Direct segmental multifrequency bioelectrical impedance analysis (DSM-BIA) is
      considered a practical, non-invasive, and relatively inexpensive method to quickly assess the
      BC27 and the estimations of BC with DSM-BIA are reported to be consistent with those of the
      DLW method also for obese patients. The joint measurement of TEE using the estimations of the
      PFR and the DLW method would serve the validation of PFR for the measurement of TEE in
      patients undergoing RYGB. PFR would become then a powerful tool for research and provide
      useful information for the design of appropriate individualized obesity treatment programs.

      Research question

      The aim of this study is to investigate changes in food preferences, total energy intake of
      the three primary macronutrients and meal patterns between obese women (BMI ≥ 35) before and
      after Roux-en-Y gastric bypass and lean (BMI ≤ 25) and obese (BMI ≥ 35) controls by means of
      PFR with the mobile application SNAQ.

      Methods

      This will be a single-centre observational case-control prospective cohort study on female
      human subjects with morbid obesity, living in Switzerland and undergoing RYGB (n=20), obese
      controls (n=20), and lean controls (n=20) before, 3, 6, and 12 months after surgery and
      beginning of the study respectively. The optimal number of participants included can be based
      on power calculations with an equivalence design and on the hypothesis that patients will
      have similar caloric intake to the lean control group one year after RYGB. The equivalent
      caloric intake between the two groups is defined by an equivalence range of 210 kcal/day with
      a SD of ±200 kcal. For achieving a power of 90% and a p=0.05 in order to exclude a difference
      of means > 210 kcal/day, n=20 participants are required per group . Patients are enrolled in
      this study if (1) they are females aged ≥ 18 years, (2) have a body mass index (BMI) ≥ 35
      kg/m2 without any previous bariatric surgery, (3) have a planned RYGB, (4) can move
      autonomously, (5) have a basic technological knowledge, (6) are fluent in German, and (7) are
      able to give their informed consent. Obese controls respect the same criteria, but have no
      plan to undergo surgery, which makes this group very hard to recruit. Lean controls have BMI
      ≤ 25 kg/m. The main purpose of the lean control group is to evaluate test stability over time
      and across multiple retesting. Patients who conform to the recruitment criteria are enrolled
      at the outpatient clinic of the University Hospital of Zurich. Obese and healthy controls are
      recruited by the study team. The study protocol is explained and written informed consent is
      obtained from all participants. The study protocol was approved by the Ethical Committee of
      the Canton of Zurich (BASEC-Nr. 2019-00952). TEE under free-living conditions is assessed
      using the DLW method. On the day before measurement, BIA is performed. On the first day of
      measurement, subjects perform urine collection at baseline and consume oral administration of
      DLW. After DLW administration, subjects collect urine respectively 3 and 4 h after
      administration and again after 7 days at the same time point of the second and third urine
      sampling . Subjects are instructed not to change their lifestyle or medication during the
      study period. Under free-living conditions for one week, overall dietary intake is registered
      by the participants using a mobile app for the photo-recognition of food items. Participants
      record their dietary intake over 7 days before, 3, 6, and 12 months after surgery.

      Data analysis

      The data of each patient will be organized as follows: time of the meal, total calories,
      total carbohydrates, proteins and fat, food group. This result has to be summed up for the
      final TEE calculation, in order to have the total amount of each variable per meal, per day
      and per week. The PFR data will be compared with DWL-based TEE for validation of the dietary
      assessment. Descriptive statistics will be used to describe demographic data, as well as to
      present meal-related information over different time periods. Change over time and from
      baseline will be assessed with ANOVA and t-tests, with correction for false discovery rates.
      Each meal-related parameter will be correlated with each other and with the 1-year weight
      loss, expressed as absolute total-body weight loss % excess BMI loss (% EBMIL). Explorative
      models will be generated using logistic regression to map meal-related information and
      optimal weight loss. All data will be analysed using RStudio.

      Limitations

      The present study has several limitations associated with the methods and the participants.
      First, the food data is self-recorded and prone to social desirability which may lead to
      inaccurate data. Indeed, the food preferences could be changed during the week of recording
      and some food items could may not be recorded. The database of food items and calories
      embedded in the app also may not be as accurate as expected. To reduce this limitation, the
      participants are asked to report any missing food items or incongruences reported by the app,
      and feedbacks are discussed with the app developer. Dietary self-monitoring is a key
      component in weight loss programs, and frequency of self-monitoring with a smartphone app is
      strongly correlated with weight loss. However, lean and obese controls of this study are not
      following any diet with the aim of weight loss and participants will record their food intake
      for a period that should not be long enough to induce changes in habits. Recent studies that
      attempted to validate the energy intake estimations by using PFR compared to the DLW method
      with obese participants found that this method was not accurate in estimating energy intake
      compared to DLW. However, in one case the TEE was measured in pregnant women who showed low
      compliance for reporting frequent intake of small meals. In the other one, the TEE was
      measured in minority preschool children whose intake was recorded by caregivers. Furthermore,
      both studies were cross-sectional studies. It is also reported that participants who use
      their own phones compared with participants who use borrowed phones capture more images and
      have higher accuracy , therefore such variable should also be considered in the data
      analysis. Technical problems with the phones may also be a source of underestimation.
      Training of the participants, constant communication and technical support must be provided
      in order to increase accuracy.

      Relevance of the expected outcome for research or practice

      This study would provide for the first time a direct and precise measurement of dietary
      intake in obese patients before and after RYGB. The direct PFR measurement with the mobile
      application SNAQ, validated by means of the DLW method, will allow to compare the energy
      intake of the three primary macronutrients per day (kcal/24h) and per meal (kcal/meal)
      between RYGB patients and controls. Furthermore, it could produce more fundamental
      information about human behaviour which will allow to translate for humans behavioural
      changes previously reported in rats. It is expected that patients will postoperatively and
      progressively adjust their relative caloric intake and food selection with a decrease of fat
      and sugars and an increase in complex carbohydrates, while non-operated controls will exhibit
      a stable, unaltered food selection and intake. The proposed research project is characterised
      by conceptual and methodological innovation. Food preferences and relative macronutrient
      intake within and between meals in patients after RYGB will be directly measured in a real
      life setting with PFR. This approach will overcome or reduce many of the limitations reported
      so far in the literature. If the expected outcome is confirmed, such a finding has the
      potential to fundamentally change clinical practice as regards to current post-bariatric
      nutritional counselling. Moreover, the results may also contribute to the development of less
      invasive interventions in the treatment of obesity and would justify a neurogenetic approach
      with animal models of obesity for mapping and studying neural circuits and linking specific
      brain activities to specific behaviours involved in obesity, as specified by the BRAIN
      initiative.
    

Intervention name(s): Recording of food intake.
Intervention type(s): Behavioral
Intervention description(s): The food intake is recorded with a photographic food recognition mobile application. The total energy expenditure is recorded with the DLW method.
Other intervention name(s): Double labeled water (DLW) method.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Morbid obesity subjects (n=40) will be recruited at the bariatric outpatient clinic of the
        department of Surgery at University Hospital Zurich during one of their preoperative
        visits. The lean control group (n=20) will be recruited by internal advertisement to
        students and employees.
      
Biospecimen description: 
      Urine samples collected after ingestion of double labeled water (DLW).
    
Keywords: Photographic Food Recognition; Morbid Obesity; Bariatric Surgery; RYGB; Food Preferences