The reinforcing value of vegetables does not increase with repeated exposure during a randomized controlled provided vegetable intervention among overweight and obese adults

Authors: Jahns, Lisa; JOHNSON, LUANN - University Of North Dakota; TEMPLE, JENNIFER - University Of Buffalo; Keim, Nancy; Casperson, Shanon; Roemmich, James

Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2016
Publication Date: 4/1/2017
Citation: Jahns, L.A., Johnson, L.K., Temple, J., Keim, N.L., Casperson, S.L., Roemmich, J.N. 2017. The reinforcing value of vegetables does not increase with repeated exposure during a randomized controlled provided vegetable intervention among overweight and obese adults [abstract]. Journal of Federation of American Societies for Experimental Biology. 31:794.4.

Interpretive Summary:

Technical Abstract: Objective: The primary aim of this randomized controlled trial is to determine whether the relative reinforcing value (RRV) of vegetables compared to a snack food can be increased through repeated exposure (incentive sensitization) to amounts of vegetables recommended by the Dietary Guidelines for Americans. The primary hypothesis is that repeated exposure to recommended amounts of vegetables will increase vegetable RRV more than exposure to the amount currently consumed. Methods: Preliminary results include 27 overweight and obese adults who reported usually consuming < 1 cup of vegetables/day. The experimental treatment consists of a two-arm, randomized, controlled, community-based, 8-wk feeding intervention trial. The two arms of the study include 1) active intervention - during which participants come to the research center twice each week to pick-up a variety of pre-packaged, minimally prepared fresh or frozen vegetables and have a skin carotenoid scan as a compliance measure. 2) attention control arm – participants receive no active intervention, but attend a similar amount of visits at the research center. Intervention participants receive recommended amounts of vegetables based upon energy needs measured by resting metabolic rate. The control group recieves no vegetables but comes to the center twice each week and has a skin carotenoid scan as an attention control. The RRV of vegetables is tested at baseline and after 8 weeks. Follow-up RRV tests occur at 12 and 16 weeks. During the RRV task, “work” is defined as how many times a person is willing to click a mouse button while playing a computer game to win points for the “reward” of a portion of a vegetable or an alternative snack cracker. Differences in groups across time in the primary outcome, RRV of vegetables, is tested using a mixed linear model with time (baseline, 8 weeks) as a within-subject factor, treatment (intervention or control) as a between-subjects factor and subject as a random effect. Baseline RRV is used as a covariate in the model. Tukey’s contrasts were used for pairwise comparison of means. Results: Participants are 80% women, with a mean BMI of 36.6. At baseline, intervention participants worked to click the mouse button a total of 450 ± 50 SE times for vegetables and 507 ± 100 times after the intervention. Control participants at baseline responded 867 ± 260 mouse clicks and after 8 weeks provided 631 ± 244 responses. There were no significant effects for total responses. An RRV of > 0.5 favors vegetables; the RRV of total responses was 0.74 at baseline for intervention participants and 0.71 after the intervention. Among controls, the RRV was 0.71 at baseline and 0.70 after 8 weeks. There were no significant effects.