Overweight children find food more reinforcing and consume more energy than do nonoverweight children

Abstract

Background: The reinforcing value of food is a reliable index of motivation to eat and energy intake. Obese adults find food more reinforcing than do nonobese adults.

Objective: The present study was designed to assess whether the relative reinforcing value of food differs as a function of weight status in 8-12-y-old children and whether the relative reinforcing value of food differs depending on the types of available nonfood alternatives.

Design: The reinforcing value of pizza (experiment 1) or snack foods (experiment 2) was measured on progressive ratio schedules of reinforcement in nonoverweight and overweight children. Experiment 2 also compared the relative reinforcing value of food and 2 nonfood alternatives: time to spend playing a hand-held video game or time to spend reading magazines or completing word searches or mazes.

Results: In both experiments, overweight children found food more reinforcing and consumed more energy than did their leaner peers. In experiment 2, the relative reinforcing value of food versus sedentary activity was higher in overweight children, but lower in nonoverweight children, regardless of the type of alternative activity available.

Conclusions: These results show that overweight children find food more reinforcing than do nonoverweight children. This individual difference was replicated in different experiments using different types of foods and food alternatives. These studies provide support for studying food reinforcement as a factor associated with overweight and obesity.

FIGURE 1

Results from experiment 1. A: Mean ( ± SEM) number of responses at each schedule of reinforcement in nonoverweight (<75th BMI percentile; n = 25) and overweight (≥90th BMI percentile; n = 20) children. Reinforcing value was analyzed with a mixed-effects regression model to compare the pattern of operant responding as a function of schedules of reinforcement for food with zBMI, sex, age, preexperimental hunger, and dietary restraint as time-invariant predictors and schedule of reinforcement (VR4 – VR256) as the time-variant predictor. There was a significant interaction of zBMI and reinforcement schedule (P <0.001), with children with higher zBMI values responding significantly more for food as the reinforcement schedules progressed. B: Mean ( ± SEM) energy consumed in the laboratory in nonoverweight and overweight children. Differences in laboratory energy intake were determined by using ANCOVA with weight status and sex as the between-subjects factors and dietary restraint score as the covariate. Overweight children made significantly more responses for food over trials (P = 0.044). *Significantly different from nonoverweight children, P = 0.003.

FIGURE 2

Mean ( ± SEM) number of points earned for food or nonfood alternatives (ie, activity) in nonoverweight (<85th BMI percentile; n = 22) and overweight (≥85th BMI percentile; n = 23) children. Reinforcing value was analyzed with mixed-effects regression models with zBMI, sex, age, preexperimental hunger, parental education, liking of magazines, and dietary restraint score as time-invariant predictors and schedule of reinforcement (VR4 – VR1024) and type of alternative (hand-held video games, mazes, word searches, and magazines) as the time-variant predictors. There was a significant interaction between weight status, type of reinforcer, and schedule of reinforcement such that overweight children found food more reinforcing than nonfood alternatives, and nonoverweight children found food less reinforcing than nonfood alternatives (P = 0.003). There was no interaction with type of activity.

FIGURE 3

Mean ( ± SEM) amount of energy consumed in the laboratory in nonoverweight (≥85th BMI percentile) and overweight (≥85th BMI percentile) children. Differences in laboratory energy intake were determined with a mixed-effects regression model with zBMI, sex, age, preexperimental hunger, and dietary restraint score as time-invariant predictors and type of alternative (hand-held video game versus mazes, word searches, and magazines) as the time-variant predictor. There was a main effect of weight status: *significantly different from nonoverweight children, P = 0.036.