Obesity
Conditions
Keywords
Taste, bariatric surgery, food preferences, reward, progressive ratio task
Brief summary
The investigators hypothesize that some of these changes in the reduced appetite after surgery may be due to alterations in taste. The aim is to compare obese patients before and after bariatric surgery (gastric bypass and banding) to define the reward value of sweet, fatty and vegetable/fruit taste in obese individuals, and how this changes after surgery.
Detailed description
Severe obesity is associated with excessive food eating and appetite. Bariatric surgery (also known as 'obesity surgery' or 'weight loss surgery') is a well known treatment for severely obese individuals. The way in which these operations achieve weight loss is not fully understood. The investigators hypothesize that some of these changes in the reduced appetite after surgery may be due to alterations in taste. The aim is to compare obese patients before and after bariatric surgery (gastric bypass and banding) to define the reward value of sweet, fatty and vegetable/fruit taste in obese individuals, and how this changes after surgery.
Interventions
None listed
Sponsors
Medical Research Council
Imperial College London
Study design
Observational model
CASE_CONTROL
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
Yes
Inclusion criteria
* BMI of 18-25 for normal weight volunteers * BMI of \>30 for obese patients
Exclusion criteria
* Pregnancy * breast feeding * substance abuse * consumption of more than 3 alcoholic units per day * severe psychiatric illness * lack of understanding of test instructions * diabetes mellitus * chronic medical conditions making a general anaesthetic unsafe * allergy to stimulus ingredients * active smoking
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Breakpoints as Assessed by Change in the Number of Mouse Clicks in the Last Completed Ratio | 2 weeks pre and 8-12 weeks post operatively for surgical patients or on two occasions 10-14 weeks apart for normal weight control group | Patients were placed in front of a computer screen and a plate of 20 chocolate candies. The following prompt appeared on the screen: You can earn food by clicking on the mouse button. Click as much or as little as you like. When you no longer want to continue, press the spacebar to stop the session.Upon completion of each ratio a message box appeared on the screen: You have earned food. Enjoy your reward and after you have swallowed it completely you may click on OK to continue with the programme.After ingesting the reward, the patients pressed the OK button in the message box only if they wished to progress to the next ratio to obtain another chocolate candy. The starting ratio was 10 clicks with a geometric increment of 2 (i.e., 10, 20, 40, 80, and so on). When the effort of pressing the mouse button was greater than the rewarding value of the chocolate candy, patients pressed on the space bar to terminate the session. This indicated that the breakpoint was reached. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Hunger | 2 weeks pre and 8-12 weeks post operatively for surgical patients or on two occasions 10-14 weeks apart for normal weight control group | Visual Analogue Scale ratings of hunger. The scale is 100mm line with two anchors at each end. Scores are recorded by making a handwritten mark that represents a continuum between not hungry at all and Extremely hungry. The score of 0 represents least hunger. The score of 100 represents extreme hunger. change in hunger levels quantified by a 100mm visual analogue scale |
| Body Mass Index | 2 weeks pre and 8-12 weeks post operatively for surgical patients or on two occasions 10-14 weeks apart for normal weight control group | change in BMI will be quantified based on the participants weight in kilograms and height in meters |
Countries
United Kingdom
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| Control Normal weight healthy volunteers | 11 |
| Bariatric Surgery obese patients due to undergo gastric bypass or gastric banding | 11 |
| Total | 22 |
Baseline characteristics
| Characteristic | Control | Bariatric Surgery | Total |
|---|---|---|---|
| Age, Customized Age | 39 years STANDARD_DEVIATION 5 | 49 years STANDARD_DEVIATION 3 | 44 years STANDARD_DEVIATION 4 |
| BMI (kg/m^2) | 23 kg/m^2 STANDARD_DEVIATION 1 | 48 kg/m^2 STANDARD_DEVIATION 2 | 35.5 kg/m^2 STANDARD_DEVIATION 1.5 |
| Ethnicity (NIH/OMB) Hispanic or Latino | 0 Participants | 0 Participants | 0 Participants |
| Ethnicity (NIH/OMB) Not Hispanic or Latino | 11 Participants | 11 Participants | 22 Participants |
| Ethnicity (NIH/OMB) Unknown or Not Reported | 0 Participants | 0 Participants | 0 Participants |
| Sex: Female, Male Female | 7 Participants | 7 Participants | 14 Participants |
| Sex: Female, Male Male | 4 Participants | 4 Participants | 8 Participants |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | 0 / 11 | 0 / 11 |
| other Total, other adverse events | 0 / 11 | 0 / 11 |
| serious Total, serious adverse events | 0 / 11 | 0 / 11 |
Outcome results
Primary
Breakpoints as Assessed by Change in the Number of Mouse Clicks in the Last Completed Ratio
Patients were placed in front of a computer screen and a plate of 20 chocolate candies. The following prompt appeared on the screen: You can earn food by clicking on the mouse button. Click as much or as little as you like. When you no longer want to continue, press the spacebar to stop the session.Upon completion of each ratio a message box appeared on the screen: You have earned food. Enjoy your reward and after you have swallowed it completely you may click on OK to continue with the programme.After ingesting the reward, the patients pressed the OK button in the message box only if they wished to progress to the next ratio to obtain another chocolate candy. The starting ratio was 10 clicks with a geometric increment of 2 (i.e., 10, 20, 40, 80, and so on). When the effort of pressing the mouse button was greater than the rewarding value of the chocolate candy, patients pressed on the space bar to terminate the session. This indicated that the breakpoint was reached.
Time frame: 2 weeks pre and 8-12 weeks post operatively for surgical patients or on two occasions 10-14 weeks apart for normal weight control group
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Control | Breakpoints as Assessed by Change in the Number of Mouse Clicks in the Last Completed Ratio | 0 Clicks | Standard Deviation 40 |
| Bariatric Surgery | Breakpoints as Assessed by Change in the Number of Mouse Clicks in the Last Completed Ratio | 320 Clicks | Standard Deviation 30 |
Secondary
Body Mass Index
change in BMI will be quantified based on the participants weight in kilograms and height in meters
Time frame: 2 weeks pre and 8-12 weeks post operatively for surgical patients or on two occasions 10-14 weeks apart for normal weight control group
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Control | Body Mass Index | -0.2 kg/m^2 | Standard Deviation 1.2 |
| Bariatric Surgery | Body Mass Index | -6.2 kg/m^2 | Standard Deviation 1.6 |
Secondary
Hunger
Visual Analogue Scale ratings of hunger. The scale is 100mm line with two anchors at each end. Scores are recorded by making a handwritten mark that represents a continuum between not hungry at all and Extremely hungry. The score of 0 represents least hunger. The score of 100 represents extreme hunger. change in hunger levels quantified by a 100mm visual analogue scale
Time frame: 2 weeks pre and 8-12 weeks post operatively for surgical patients or on two occasions 10-14 weeks apart for normal weight control group
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Control | Hunger | 20 mm | Standard Deviation 30 |
| Bariatric Surgery | Hunger | -60 mm | Standard Deviation 30 |