Validating a human behavioral economic choice paradigm for
assessing food demand among post-weight loss surgery patients
Shannon Clark¹, Summar Reslan¹, Karen K. Saules¹, and Mark K. Greenwald²
Eastern Michigan University, Department of Psychology¹
Wayne State University, Department of Psychiatry and Behavioral Neurosciences²
Introduction
Most human behavioral economic research has focused on
drug choice. For example, within this theoretical framework, the
reinforcing value of drugs has been assessed by measuring the
amount of work a participant is willing to do to gain access to a
preferred drug. Recently, we validated this approach in a
human laboratory model of food-appetitive behavior (Reslan,
Saules, & Greenwald, in press). We now expand this method to
post-weight loss surgery (WLS) patients, because food choice
may impact weight regain after WLS.
Method
Participants (N = 11) were at least 24 months post-WLS and all
were above the 50% Excess Weight Loss (and maintained)
criteria. Most (n=10) had undergone Roux-en-Y WLS, and one
had undergone the gastric sleeve procedure. Participants completed a screening survey to ensure that those recruited would
be non-pregnant (to avoid pregnancy-related effects on food
preference) and without carpal tunnel syndrome (because the
laboratory task involved computer “mouse”-pressing). All
participants liked and were non-allergic to all food items offered
during experimental sessions. Participants completed two
sessions that imposed exponentially increasing prices to earn
the same unit amount of each food. All food was consumed
post-session.
 Task 1:
 High-Fat/High-Carb (Original Pringles) vs. No-Fat/HighCarb (Fat-Free Pringles)
 Task 2:
 High-Fat/High-Carb (Original Pringles) vs. No-Fat/LowCarb (Baby Carrots)
Results
For Task 1, mean breakpoint for No-Fat/High-Carb chips was 7.7
times greater than for High-Fat/High-Carb chips (i.e. 693.0 vs.
93.3). For Task 2, mean breakpoint was 3.7 times greater for
No-Fat/Low-Carb Carrots than for High-Fat/High-Carb chips (i.e.
571.5 vs. 154.4). As seen in the figures, demand curves fitted to
the data for the group-percent choice means exhibit a parallel shift
or a change in demand intensity, but no significant difference in
demand elasticity (curvature). Least-squares regression was used
to estimate the overall fit of the demand curves to the data. According to these analyses, demand curves were a good fit (r ² = .84 to
.96).
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Response Requirement
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Figure 3. Successful WLS patients’ demand for High-Fat/HighCarb food versus No-Fat/Low-Carb food again indicates that the
more healthful option is selected more often, regardless of price.
Discussion
As seen in the results, the healthful option was selected more,
independent of price, by our sample of successful WLS patients.
Thus, our findings provide support for the use of behavioral
economic procedures to better understand outcomes following
WLS. In future studies, we hope to use this method to predict WLS
outcomes prospectively. Our understanding of the factors that
influence outcomes following WLS is in its infancy, but our study
begins to show how the parameters of food choice may relate to
these outcomes. This investigation was limited by a small sample
size and relatively homogeneous sample of successful WLS
patients. Although we predict that unsuccessful patients will work
harder for unhealthful food, we were unable to test this hypothesis. Future research should expand these findings to participants
with more heterogeneous weight loss outcomes.
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Trial
Figure 1. Response requirement (i.e., number of mouse button
presses) increased exponentially.
Figure 2. Successful WLS patients’ demand for High-Fat/High-Carb
food versus No-Fat/High-Carb food indicates that the more healthful
option is selected more often, regardless of price.
Contact: sclark42@emich.edu
Presented at the 2012 Annual Meeting of The Obesity Society