Unintentional eating. What determines goal-incongruent chocolate consumption?

Abstract

Overeating can be automatically triggered by the presence of palatable food. When presented with an opportunity to consume unlimited chocolate under the guise of a consumer study, chocolate consumption in individuals (n = 62) with healthy dietary intentions could be predicted from a psychological measure of cognitive inhibition. Individuals who were less able to suppress goal-incongruent responses in an established inhibitory task: (a) ate more chocolate and (b) had a higher body mass index than others suggesting that these individuals were less able to exert dietary control in the presence of palatable but intention-incongruent foods.

Introduction

Although snacks are theoretically supplementary to the main diet, they represent a major source of caloric intake (Summerbell, Moody, Shanks, Stock, & Geissler, 1995). Snack foods are typically highly palatable and ‘energy-dense’ (i.e. they contain many calories for the portion size) but have little nutritional value. Snacking on energy-dense foods is associated with a higher caloric intake and problems in weight control (Conner and Norman, 1996, McCrory et al., 1999).

What drives overconsumption of energy-dense snacks? Animal models of eating behaviour suggest that simply increasing the availability of preferred, highly palatable foods leads to overeating (Tordoff, 2002). In Western society, energy-dense snacks are readily available in a vast array of food and non-food outlets and can be purchased through vending machines at times and locations where other foods cannot. This ready availability of highly palatable but unhealthy foods means that consumers attempting to eat healthily must constantly choose between effortfully enacting their healthy intentions and effortlessly indulging in palatable but unhealthy snack foods.

Hofmann, Friese, and Strack (2009) describe such instances of temptation as tug-of-war conflicts between impulses and self-control. Impulses to indulge are aimed at short-term gratification and, unless challenged, can operate largely without conscious awareness. Impulses are thought to arise from the automatic activation of associative networks linking behaviours to known outcomes, and operate unless effortfully suppressed by the conscious activation of a higher-level, goal-oriented system (Strack & Deutsch, 2004).

In such a tug-of-war between impulses and self-control, the behavioural outcome will depend on the relative strength of activation of each system. While limited control resources would be expected to bias behaviour in the direction of the impulsive system, plentiful control resources should bias behaviour in the direction of higher-order goals as the resources needed to suppress the automatic response pattern would be available. If this is the case, then individual differences in the strength and availability of cognitive control resources should be related to whether or not people choose to eat in line with their dietary intentions on presentation of palatable but intention-incongruent foods.

Cognitive or ‘executive’ control processes are the higher-order processes responsible for the planning, initiation, sequencing, and monitoring of complex goal directed behaviour (Royall et al., 2002). At the group level, adults with elevated body mass index and obese children and adults have been shown to exhibit weak executive control (Braet et al., 2007, Cserjesi et al., 2007, Cserjesi et al., 2009, Gunstad et al., 2007) suggesting that poor executive functioning is related at some level to dietary behaviour.

The few studies examining links between executive control and dietary behaviour at the individual level suggest that individual differences in executive control are indeed predictably related to whether or not people eat in line with their intentions. Hall, Fong, Epp, and Elias (2008) found that people with good executive control were more likely to eat the amount of fruit and vegetables they intended than those with weak executive control, and data from our own lab (Allan, Johnston & Campbell, in press) has demonstrated that the discrepancy between intended and actual consumption of both fruit and vegetables and high-calorie snacks over several days can be prospectively predicted from individual differences in executive control.

While this previous work has focussed on the role of executive control in the implementation of intentional eating behaviours, the present study turns attention to the suppression of ‘unintentional’ eating behaviours, and specifically to the role of cognitive inhibition in suppressing eating that conflicts with dietary intentions. In today's obesogenic environment, where palatable, high-calorie foods are readily available, successful dietary control may rest largely on the ability to inhibit or resist indulgence in intention-incongruent eating.

Participants who intended to avoid high-calorie snacks were presented with the opportunity to eat a highly palatable but high-calorie food (chocolate) during a mock consumer rating task. The amount of chocolate consumed was predicted from their performance on a set of executive control tasks. We anticipated that weak executive control in general, but poor inhibitory control in particular, would be associated with greater ‘unintentional’ consumption of the available chocolate and a higher BMI.