Sensitization and habituation of motivated behavior in overweight and non-overweight children

Abstract

The rate of habituation to food is inversely related to energy intake, and overweight children may habituate slower to food and consume more energy. This study compared patterns of sensitization, as defined by an initial increase in operant or motivated responding for food, and habituation, defined by gradual reduction in responding, for macaroni and cheese and pizza in overweight and non-overweight 8-12 year-old children. Non-overweight children habituated faster to both foods than overweight children (p = 0.03). All children recovered motivated responding for a new food (chocolate). Overweight children consumed more energy than non-overweight children (p = 0.0004). Children who showed a sensitization in responding consumed more food (p = 0.001), and sensitization moderated the effect of overweight on habituation, with slower habituation for overweight children who sensitized (p < 0.0001). This study replicates previous data on overweight/non-overweight differences in habituation of food and of energy intake, and provides new information that individual differences in sensitization and habituation of motivated responding to food cues may be associated with a sustained motivation to eat, resulting in greater energy intake.

Figure 1

Differences in motivated responding (mean ± SEM) on variable ratio 120 second schedules of reinforcement for non-overweight versus overweight children (Figure 1A) and for pizza and macaroni and cheese (Figure 1B). Mixed regression models showed both overweight status (p = 0.03) and type of food (p = 0.008) influenced the rate of habituation. Recovery of responding was shown when chocolate was presented as a novel food after the 12^th 2 minute time block (p < 0.001).

Figure 2

Energy consumption (mean ± SEM) during the habituation and recovery phases, and total energy intake across both phases for overweight and non-overweight children. Overweight children consumed greater energy during the habituation phase (p < 0.001) and for total energy consumption (p < 0.001).

Figure 3

Motivated responding (mean ± SEM) on variable ratio 120 second schedules of reinforcement for children who sensitized and those who did not for the four definitions of sensitization. In each case there were significant differences in the rate of habituation comparing those who sensitized versus those who did not sensitize (p < 0.001). The n that met criteria for each definition is shown in each graph, along with the average habituation curve of all participants.

Figure 4

Motivated responding (mean ± SEM) on variable ratio 120 second schedules of reinforcement for overweight or non-overweight children who did or did not sensitize. Sensitization interacted with overweight status to influence responding across time blocks (p < 0.001). No differences in the rate of habituation were observed between overweight and non-overweight children who did not sensitize, but slower habituation was observed for the overweight in comparison to the non-overweight children (p = 0.003).

Figure 5

Energy consumption (mean ± SEM) for overweight and non-overweight subjects who sensitized and did not sensitize during the habituation and recovery phases, as well as total energy intake. Children who sensitized consumed more food during the habituation phase (p = 0.001) and for total energy intake (p = 0.001). No interaction of sensitization and weight status on energy intake was observed.