Microstructural Analysis of Ingestive Behavior After Roux-en-Y Gastric Bypass - Pilot
Condition: Meal; Obesity, Morbid; Food Deprivation; Bariatric Surgery; Roux-en-y Gastric Bypass; Ingestive Microstructure; Drinking Behavior; Drinkometer
MeSH terms: Obesity, Morbid; Drinking Behavior
Study type: Observational

Summary: 
      The ability to assess ingestion in fine detail over the time course of a liquid meal allows
      for comparison of early and late meal features of drinking and may help dissociate
      manipulations (surgical, neural, pharmacological, etc.) that affect orosensory properties
      from those that are modulating postoral processes in the control of intake.

      The aim of the study is to asses microstructural changes in liquid meal intake over 1-year in
      severely obese patients after Roux-en-Y gastric bypass (RYGB).
    

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 hormone 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 taste preferences.
      Initial insights on food intake and appetite can be provided by indirect measures such as
      verbal report of energy intake, food diaries, and dietary recall questionnaires. However,
      indirect measures are vulnerable to inaccuracy and, at best, only offer an estimate of the
      target behavior. Such methodological limitations can be improved by complementing existing
      findings with direct measures of feeding and drinking. There are only very few studies to
      date that have applied direct measures of ingestive behavior in BS patients. These studies
      focused mainly on macronutrient composition within a cafeteria diet and on some motivational
      aspects of appetite 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 novel drinkometer for humans, which may have great
      utility in investigations of the specific behavioral variables that underlie the
      dysregulation of appetite control in morbid obesity, and also to specify neural effects of
      various medical or surgical weight-loss interventions.

      The aim of this exploratory pilot study is to observe the ingestive microstructure of a
      liquid meal intake before and several occasions after RYGB. Observed values may serve as
      basis for designing future observational studies in the field of obesity research.

      Methods

      Prospective observational controlled cohort pilot study in severely obese patients scheduled
      for RYGB. 11 patients and 10 normal-weight controls will be recruited to consume a
      calorically dense standardized refrigerated liquid meal (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, taste preference and participants will
      estimate their intake at the end of each session. Time points for patients: pre-operatively,
      postoperative 1 week, 1-3-6-12 months. Time points for control group: baseline, 1-3-12
      months. Due to major differences in ingestive microstructure, only female participants will
      be included in the study.

      Satistical 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, as well as
      ANOVA, t-tests and Wilcoxon signed rank test in R 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 after
      BS. Results will inform on the range of values that can be observed in this patient
      population and will serve as a basis to accurately power future studies in this field.
      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 no difference in the ingestive behavior between patients before
      and after RYGB and in comparison to lean controls when the high-sugar high-fat stimulus is
      consumed for the first time. The investigators also do not expect an effect of RYGB on the
      number of sucking events within the first minute of the test session. As initial suck rate
      reflects the consummatory behavior in response to a given stimulus and thus indicate the
      initial motivational state toward this stimulus, the lack of RYGB-induced changes in this
      microstructural parameter would suggest that RYGB does not change the palatability of the
      stimulus. In line with this, the investigators further expect that suck rate during
      consumption of the fluid will decrease as a function of meal progress and with progressing
      postoperative time in patients after RYGB, but not in lean controls. 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: Case-Control
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Adult females with severe obesity and scheduled to undergo RYGB