Elsevier

Appetite

Volume 107, 1 December 2016, Pages 323-329
Appetite

Licence to eat: Information on energy expended during exercise affects subsequent energy intake

https://doi.org/10.1016/j.appet.2016.08.107Get rights and content

Abstract

An acute bout of exercise, compared with no exercise, appears to have little influence on subsequent energy intake (EI), resulting in short-term negative energy balance. Whereas the labelling of food is evidenced to influence EI, little research has focused on how EI is affected by framing acute exercise in different ways. To explore this, 70 healthy, mostly lean, male and female participants in the current study completed a set amount of exercise (estimated energy expenditure (EE) 120 kcal), but were informed on three occasions before and after the exercise that they had expended either 50 kcal or 265 kcal. An ad libitum test meal, comprising orange juice, tortilla chips and chocolate chip cookies, was then presented after a 10-min break to assess subsequent EI. Measures of hunger and dietary restraint were also completed. Greater EI, primarily driven by chocolate chip cookie consumption (p = 0.015), was observed in participants receiving 265 kcal EE information. Hunger ratings were significantly lower in the 265 kcal EE information group than in the 50 kcal group following the test meal (p = 0.035), but not immediately after the exercise. These results support an interpretation that higher EE information (265 kcal) provides participants with a greater ‘licence to eat’ when palatable foods are accessible. Tentative evidence for a moderating effect of dietary restraint was observed, indicating a greater influence of EE information in participants with lower restraint. The findings of the current study suggest that the provision of EE information (e.g., through mobile device apps) could be counter-productive to healthy weight management.

Introduction

Physical activity has been suggested to influence weight by altering the balance between energy expenditure (EE) and energy intake (EI) (Martins, Morgan, & Truby, 2008). In this context, it is significant that the effects of an acute bout of exercise on subsequent EI and appetite are variable, but on average very small (Schubert, Desbrow, Sabapathy, & Leveritt, 2013). A greater understanding of this relationship is therefore important due to its implications for weight control (King, Hopkins, Caudwell, Stubbs, & Blundell, 2008).

A recent meta-analysis concluded that acute exercise has a trivial effect on absolute EI (Schubert et al., 2013). The reason for this is contended to be that the energy expended in acute exercise is trivial compared with the total energy stored in the body (Rogers & Brunstrom, 2016). A negative energy balance is induced due to this lack of compensation, and reflects a lower EI relative to the expenditure. However, Schubert and colleagues' conclusion masks considerable variability in the research findings. One review indicated that 65% of studies reported no change in EI following exercise, whereas 16% observed a reduction and 19% an increase (Blundell & King, 1999). This variability may be partly due to differences between studies, such as gender, exercise intensity and macronutrient composition of the test foods (Martins et al., 2008).

Research suggests the relationship between EE and EI is influenced by dietary restraint (Hawks, Madanat, & Christley, 2008a). Overall, evidence indicates that high dietary restraint is associated with a larger negative energy balance following acute exercise (King et al., 2012, Lluch et al., 2000). This larger effect may occur due to exercise assisting restrained individuals in controlling their eating behaviour (King, 1999). According to the goal conflict model of eating, restrained eating behaviour is determined by two opposing goals, eating enjoyment and weight control (Stroebe et al., 2008, Stroebe et al., 2013). The more active goal is argued to inhibit the other, and consequently exerts greater influence over eating behaviour. For example, if the eating enjoyment goal is more active, a restrained eater may violate their weight control goal and overeat. Goals are proposed to become more or less active when primed by relevant cues (e.g., eating enjoyment activated by palatable foods). Therefore, cues that prime weight control should inhibit eating enjoyment. This could explain the large negative balance observed in restrained individuals following exercise, which may prime the weight control goal.

This proposed priming effect reflects how external stimuli can influence EI (Martins et al., 2008). Research has indicated that the way in which food is labelled or framed can influence intake. For example, higher EI has been reported for foods labelled as ‘low-fat’ and ‘fitness’ (Koenigstorfer et al., 2013, Wansink and Chandon, 2006). Exercise-related primes (e.g., posters, videos) have also been indicated to influence subsequent EI, although the direction of this effect is ambiguous. Specifically, EI has been shown to both increase (Albarracin, Wang, & Leeper, 2009) and decrease (Stein et al., 2016, van Kleef et al., 2011) following exercise-related primes. Furthermore, individual differences are suggested to play an important role in this effect (e.g., self-reported exercise levels) (Stein et al., 2016).

Dietary restraint is also argued to influence how susceptible consumers are to the way in which a food is presented (i.e., labelled). For example, restrained participants have been found to consume more at a subsequent meal when a drink was described as having a high energy content, despite containing the same energy as a comparison (Mills and Palandra, 2008, Polivy, 1976). This pattern of eating is referred to as ‘counter-regulatory eating’ and is argued to occur once a restrained eater's dietary goal is violated (Herman & Polivy, 1984). In the example above, restrained eaters may have evaluated their weight control goal to have been violated due to the drink's high energy content label. As a result of having already violated this goal, it is suggested that the restrained eaters had less reason to further control their EI, and therefore they overate.

The aim of the current study is to draw together the previously detailed research which investigated two factors that are argued to influence subsequent EI – i.e., an acute bout of exercise, and labelling. Specifically, the current study aims to explore whether the way in which exercise is framed influences subsequent EI. Two recent studies have investigated this by framing exercise in qualitatively distinct ways (Fenzl et al., 2014, Werle et al., 2014). Participants in Werle and colleagues' study consumed less dessert and fewer hedonic snacks when a walk was framed as fun rather than exercise. This was interpreted as participants having a reduced need to compensate after the fun walk, due to experiencing greater enjoyment. In Fenzl and colleagues' study, cycling framed as ‘fat-burning’ – rather than ‘endurance’ – was associated with an increase in subsequent EI in participants who exercised due to externally imposed self-regulation. Associations of ‘fat-burning’ with greater EE were argued to give these participants a greater licence to eat. These two studies provide evidence that the connotations evoked from the way exercise is framed can influence compensatory eating behaviour.

The current study aims to develop the findings of these studies and to explore whether quantitatively distinct, but qualitatively comparable labels influence subsequent EI. Due to the ubiquity of wearable devices that estimate calorie-expenditure during exercise, the effect of this information on subsequent EI warrants investigation. In order to explore the effect of this labelling, all participants completed an acute bout of cycling until the same calorimetric target was reached (estimated EE 120 kcal). However, they were informed as having expended either 50 kcal or 265 kcal. Therefore, both labels represent EE, but of different quantities. The influence of these EE information labels on hunger ratings and subsequent EI was then assessed. Based on Fenzl and colleagues' findings, it was predicted that participants would have greater subsequent EI in the 265 kcal condition – which represented higher EE – compared with the 50 kcal condition.

The moderation by dietary restraint in the relationship between EE information and EI was also investigated. From the perspective of the goal conflict model of eating (Stroebe et al., 2013), completing any amount of exercise could be conceptualised as assisting restrained eaters by priming their weight control goal (and inhibiting eating enjoyment). This could explain the aforementioned findings that higher restraint is associated with a greater negative energy balance following acute exercise (King et al., 2012, Lluch et al., 2000). As such, it was predicted that restrained participants would not differ between the EE information conditions (50 kcal, 265 kcal). In contrast, less restrained participants were predicted to have higher subsequent EI in the 265 kcal EE information condition, in line with the findings of the previous exercise-labelling research.

Section snippets

Participants

Seventy healthy, mostly lean people (24 male, 46 female) participated in the study. Inclusion criteria were 18–65 years old, non-smoker or light smoker (≤5 cigarettes a day), no history of eating disorders, no food allergies or intolerances, not vegan, not taking drugs which may influence appetite (except oral contraceptives), and willing and able to complete 15–25 min of cycling. Ethical approval was obtained from the University of Bristol's Faculty of Science Human Research Ethics Committee.

Participant characteristics

Participant characteristics are summarised by EE information group in Table 2. Participants in both conditions were well-matched for key characteristics, including age, gender, BMI, restraint and baseline hunger. Exercise duration was also very similar between groups.

All participants completed the required exercise and were included in subsequent analyses.

EE information and gender effects on subsequent EI

As shown in Fig. 1, participants consumed more overall, and of each test item, when presented with 265 kcal EE information compared with

Discussion

This novel research provides evidence that information about the energy expended during exercise affects subsequent EI. A small effect of EE information on overall EI, which approached statistical significance, supported the initial prediction and reflected greater consumption in participants who received high (265 kcal) EE information compared with those who received low EE information (50 kcal). A statistically significant medium effect of EE information on cookie EI revealed that

Conclusions

This novel research indicated that EE information relating to an acute bout of exercise can influence subsequent EI. This was interpreted as high EE information providing a greater licence to eat. The findings strongly support the need for further investigation, as they have important implications for weight control and conducting research into the effects of exercise on subsequent EI.

Sources of support

This study was financially supported by the School of Experimental Psychology, University of Bristol. The funding source had no involvement in the study design, collection, analysis or interpretation of the data, the writing of the report, or the decision to submit the article for publication.

Part of the work leading to the completion of this paper received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant

Disclosure

The authors have no conflict of interests to disclose.

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