Microstructure of Ingestive Behavior and Body Weight Loss After Roux-en-Y Gastric Bypass
Condition: Obesity; Food Deprivation; Bariatric Surgery; Roux-en-y Gastric Bypass; Ingestive Microstructure; Ingestive Behavior; Drinkometer
MeSH terms: Weight Loss; Body Weight
Study type: Observational

Summary: 
      Studies of appetitive behavior in humans after RYGB have produced ambiguous results. It
      therefore remains unclear whether there are fundamental shifts in the palatability of
      high-fat and sugary foods after RYGB or simply a decrease in the appetitive drive to ingest
      them. Moreover, learning processes may play a role as changes in diet selection progress with
      time in rats after RYGB. However, direct measures of an altered food selection in humans
      after RYGB are rare and both the durability of the phenomenon as well as the role of
      experience for changes in food selection remain elusive.
    

Detailed description: 
      Introduction Bariatric surgery (BS) is currently the most effective treatment of severe
      obesity. BS has a pleiotropic effect on the body, involving changes in basic metabolic rate,
      gut hormones and bile acid levels, intestinal nerve signaling and microbiota composition.
      Overall, patients report to eat less, to feel less hungry and they often change their food
      preferences. Initial insights on food intake and appetite can be provided by indirect
      measurements such as verbal report of energy intake, food diaries, and dietary recall
      questionnaires. However, indirect measurements are vulnerable to inaccuracy and, at best,
      only offer an estimate of the patients' real behavior. Such methodological limitations can be
      improved by complementing existing findings with direct measurements of eating and drinking.
      There are only very few studies to date that have applied direct measurements of ingestive
      behavior in BS patients. These studies focused mainly on macronutrient composition within a
      cafeteria diet and on some motivational aspects of appetitive behavior. This might be due to
      the fact that the assessment of the temporal organization of ingestive behavior within a meal
      in humans poses significant methodological and conceptual challenges to researchers and study
      design. The investigators have recently developed and validated a drinkometer for humans,
      which may have great utility in the investigation of the specific behavioral variables that
      underlie the altered appetite control in obesity, and also to specify neural effects of
      various medical or surgical weight-loss interventions.

      The aim of this exploratory pilot study is to investigate a possible correlation between the
      microstructure of ingestive behavior and body weight loss in patients after Roux-en-Y gastric
      bypass with a follow-up of 5 years.

      Methods Prospective observational study in patients that already received a RYGB. 50 patients
      will be recruited to consume a ready-to-drink, energy-dense oral nutritional supplement
      (product: Resource 2.0+fibre, Nestle, Vevey, Switzerland) in a food deprived state, until
      reaching satiety. The novel drinkometer will be used to measure ingestive microstructure and
      overall intake, and anthropometric parameters (weight, height) will be measured as well.
      Visual analogue scales will be used to assess self-reported hunger, thirst, fullness, liking,
      nausea, and pain. The participants will be asked to estimate their intake at the end of each
      session. The study visits will take place at each postoperative yearly control visit. Only
      for one subgroup of 30 patients, one year after surgery, one second study visit will be
      organised after an interval of two weeks from the first visit. In order to avoid sex-driven
      major differences in ingestive microstructure, only female participants will be included in
      the study.

      Statistical analysis The drinkometer data will be processed and filtered by an in-house
      developed algorithm in Matlab 2017 software. Results will be analysed using descriptive
      statistics and statistical tests in RStudio software version 3.5.1.

      Potential outcomes Any comprehensive understanding of how BS affects food intake requires a
      detailed analysis of the ingestive behavior itself, not simply the measurement of the outcome
      of the behavior. In other words, the information on how the food is consumed is equally or
      even more important than the information on how much food has been ingested. To the best of
      our knowledge, this is the first time that drinking microstructure in humans will be recorded
      and analyzed with a five-year follow-up in BS patients. Results will confirm if, in the long
      term, the microstructure of ingestive behavior might have a correlation with body weight loss
      or regain and hence be used as a predictor of surgery outcome. Further, this exploratory
      study may generate hypothesis on behavioral changes that occur following BS. Any treatment
      that affects total intake - e.g. BS - can be entirely viewed as function of its single
      components such as size and number of sucking bursts which then can provide relevant
      information e.g. on the motivational aspects of the ingestive behavior. The investigators
      expect to find at least two type of ingestive behaviours among study participants, one that
      would correlated with sustained body weight loss and one that would correlate with body
      weight regain.

      Regardless of which outcomes are obtained, this innovative experiment will be a critical and
      a novel test of the explicit experience of humans with a high-sugar high-fat liquid meal
      after RYGB and its potential role for the understanding possible mechanisms determining
      postoperative outcomes, such as weight loss.
    

Intervention name(s): Roux-en-Y Gastric Bypass
Intervention type(s): Procedure
Intervention description(s): Laparoscopic surgical procedure
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Adult females with severe obesity that underwent RYGB