Study design for a randomized controlled trial to increase the relative reinforcing value of vegetable consumption using incentive sensitization among obese and overweight people

Authors: Jahns, Lisa; Roemmich, James

Submitted to: Contemporary Clinical Trials
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2016
Publication Date: 8/24/2016
Citation: Jahns, L.A., Roemmich, J.N. 2016. Study design for a randomized controlled trial to increase the relative reinforcing value of vegetable consumption using incentive sensitization among obese and overweight people. Contemporary Clinical Trials. 50:186-192.

Interpretive Summary: Federal dietary guidance recommends consumption of a variety of vegetables, but Americans do not consume enough of them. Studies have attempted to increase consumption of vegetables but with limited success. Many people cite that barriers to consuming enough vegetables includes not remembering to buy them, the inconvenience of preparing them, and not knowing how to prepare them. In this manuscript, we present the design of a study that will attempt to overcome some of these barriers. This 16-week, randomized, controlled, community-based feeding study seeks to use repeated exposure to amounts of vegetables recommended by federal guidance for 8 weeks to increase the primary outcome of the relative reinforcing value of vegetables compared to a snack food, or whether a person is more willing to work to obtain a vegetable snack compared to a snack food. Secondary outcomes include: 1) Determining other factors that may affect vegetable consumption such as genetic polymorphisms in taste and whether or not a person is able to delay gratification. 2) Determine whether paricipants added vegetables to their usual diet or substituted vegetables for food groups reported in a consumption log and by diet recall. 3) Determine whether reductions in body fat are associated with substitution of vegetables in the diet. 4) Determine if markers of bone turnover change. 5) Asess changes in self-reported secondary outcomes measured by questionnaire such as self-efficacy to eat vegetables. The results of this study will provide information about the influences on the individual choice to consume recommended amounts of vegetables. The understanding gained will help increase the effectiveness and sustainability of behavior-based interventions focused on improving vegetable intake. This information may also be used to assist in setting dietary guidance targets for the amounts and types of vegetables Americans can, and should, consume.

Technical Abstract: Federal dietary guidance recommends consumption of a variety of vegetables, but Americans only consume a small fraction of recommended amounts. Studies have attempted to increase consumption with modest results. In this manuscript, we present the protocol for a study that applies incentive sensitization theory to improve vegetable intake. This 16-week, randomized, controlled, community-based feeding study seeks to use repeated exposure to amounts of vegetables recommended by federal guidance for 8 weeks to increase the primary outcome of the relative reinforcing value of vegetables compared to a snack food. Secondary outcomes include: 1) Determine potential moderators of incentive sensitization of vegetables, including genetic polymorphisms associated with food reinforcement and obesity, PROP tasting status, and delay discounting. 2) Determine whether paricipants added vegetables to their usual diet or substituted vegetables for food groups reported in a consumption log and by diet recall. 3) Determine whether reductions in adiposity are associated with substitution of vegetables in the diet. 4) Asess changes in self-reported secondary outcomes measured by questionnaire such as self-efficacy to eat vegetables. The results of this study will provide information about the drivers of individual choice to consume recommended amounts of vegetables. The understanding gained will help increase the effectiveness and sustainability of behavior-based interventions focused on improving vegetable intake. This information may also be used to assist in setting dietary guidance targets for the amounts and types of vegetables Americans can, and should, consume.