Do low-calorie sweetened beverages help to control food cravings? Two experimental studies
Introduction
Low-calorie sweetened (LCS) beverages have emerged as a strategy to reduce total energy intake, providing sweet taste without additional calories and thereby potentially assisting in weight loss [36,38]. Despite their popularity, the influence of LCS beverages on energy intake and weight maintenance has been a contentious issue. Some argue that LCS beverages encourage a preference for hedonically pleasing food and increase the risk for weight gain and obesity [24,37,45,47], although this may be a non-causative association. Indeed, a recent systematic review found that consumption of LCS beverages, when used as a substitute for sugar, is associated with reductions in energy intake and body weight [41]. Given this controversy, understanding the motivations behind consumption of LCS beverages is of importance. However, little is known about the underlying psychological drivers behind frequent consumption of LCS beverages and how these psychological factors impact on eating behaviour.
To address this research gap, Appleton and Conner [4] previously investigated the characteristics associated with frequent consumption of LCS beverages. They found that frequent consumers of these beverages are typically overweight but also have high dietary restraint and body weight concerns relative to non-consumers of LCS beverages. Restrained eaters are motivated to control their weight by restricting their food intake; however, they are often unsuccessful in these attempts and their eating behaviour is characterised by periods of food restriction and disinhibited eating [25,32]. The goal conflict model proposes that dietary restraint is difficult because these individuals are attempting to juggle two conflicting goals; their hedonic goal of enjoyment of eating while also satisfying their long-term goal of weight maintenance [44]. This is a challenge for dieters because low-energy, “diet” foods are often less hedonically pleasing than foods with higher calorie contents [19].
Drawing on the above, it is plausible that LCS beverages may benefit some individuals because these products are able to satisfy food cravings and/or hedonic desire for sweetness while also enabling maintenance of dieting goals (thereby realigning previously conflicting goals). However systematic investigation of this has yet to be conducted and the mechanisms for how LCS beverages might influence energy intake are unclear.
One possibility is that LCS beverages may act as a “diet prime”, reminding consumers of their dieting motivations and thereby helping to regulate their eating behaviour. While this has not been investigated specifically for LCS beverages, several studies have demonstrated that exposing participants to cues linked with their longstanding diet goals can trigger goal-directed behaviour [11,12,22]. For example, restrained eaters do not overeat following pre-exposure to palatable food cues when they are reminded of their dieting goal ([40]; see also Anschutz et al. [2], for comparable findings). However, it is important that the primed goal is motivationally relevant to that individual, in that given situation ([1,17,23,39,52]). Given this link, it is plausible that exposure to LCS beverages may similarly act as a diet prime for frequent consumers of these beverages and thereby enable them to pursue their long-term weight maintenance goals even in situations in which short-term hedonic goals typically prevail. As a result, individuals may feel more in control and less guilty over their eating. Given that negative affect is often associated with increased consumption or emotional eating ([16,20,26]), determining whether consumption of LCS beverages reduces feelings of guilt and increases perceived behavioural control would also be meaningful.
In line with the goal-conflict model, another possibility is that the presence and availability of LCS beverages acts as a highly salient hedonic cue due to their association with a rewarding experience (i.e. sweet taste). According to incentive-motivational models, repeated exposure to stimuli associated with food reward results in biased attention towards these and any other relevant stimuli (see [21]). As a result of this, we would expect frequent consumers of LCS beverages to exhibit a bias in attention towards LCS beverages, and this bias may be further amplified under conditions when hedonic eating motivations are activated. Consistent with this idea, Kemps and Tiggeman [28] found that participants who were experimentally induced into a temporary state of food craving showed increased attentional bias to chocolate-related pictures, relative to the control condition (see also [43,51], for similar findings). Thus, if LCS beverages are associated with hedonic eating motivations in frequent consumers, we would expect to see an amplified attentional bias towards cues associated with LCS beverage stimuli, particularly when hedonic motivations (i.e. food cravings) are primed.
The overarching aim of the present research was to determine the psychological mechanisms underpinning the effect of LCS beverages on eating behaviour. Specifically, we investigated the effect of priming hedonic eating goals, via a chocolate craving manipulation, on ad libitum energy intake in frequent and non-consumers of LCS beverages. It is well-established that food cue exposure and craving increase food intake [9], therefore in Study 1, we hypothesised that energy intake would be greater after the craving manipulation relative to the control manipulation in non-consumers. However, we predicted that frequent consumers would be protected from this effect due to the availability of LCS beverages in the ad libitum eating context (Hypothesis 1). We also examined attentional bias towards LCS beverage-related stimuli following the craving or control manipulation. We predicted that frequent consumers, but not non-consumers, would show an attentional bias to LCS beverage stimuli and that this bias would be amplified when frequent consumers were in a state of craving (Hypothesis 2). Study 2 sought to replicate Study 1 while also directly manipulating the availability of LCS beverages and including measures of guilt and perceived behavioural control over eating.
Section snippets
Participants
One hundred and twenty university staff and students (Mean age 31.44 ± 8.54 years) were recruited to take part in a study investigating the relationship between beverage consumption and behaviour. Prior to attending the laboratory session, participants were identified and classified as frequent and non-consumers of LCS beverages according to a self-reported online Food Frequency Questionnaire (FFQ) assessing consumption of a range of beverages (see [4]). Participants were classified as frequent
Participant characteristics
Due to technical problems with the eye-tracker, data from 5 participants were lost. Four participants had excessive missing data from the VPT (>25% reaction times missing) and were also excluded; the remainder had <5% of data missing. Nine additional participants were therefore recruited to replace the lost data. Participant characteristics of the final sample are provided in Table 1. Independent samples t-tests confirmed that frequent consumers had significantly higher BMI, restraint,
Participants
Participants (N = 172) were frequent consumers of LCS beverages, as determined using the Appleton and Conner [4] FFQ which was completed during an online pre-study screening questionnaire. In a 2 × 2 between-subjects design, participants were randomly allocated either to the craving or control condition, and the LCS available or LCS unavailable condition, generating four independent groups. We powered the study (80% power) using GPOWER 3.1 to detect a medium-large effect size (f = 0.35, on the
Participant characteristics
One-way ANOVAs revealed no differences between the experimental conditions with regard to age, BMI, restraint, emotional and external eating traits, indicating that all groups were evenly matched (ps > 0.105). Participant characteristics are provided in Table 2. A chi-square analysis confirmed that there was no difference in the number of males and females between conditions, χ2(3) = 3.81, p = .283.
Craving ratings indicated that the craving manipulation was effective in inducing craving in
Conclusion
LCS beverages did not consistently protect consumers from craving-induced increases in food intake. However, frequent consumers consumed fewer calories overall when LCS beverages were available (relative to unavailable), as well as experiencing more control over their food intake, greater meal enjoyment and less guilt. These findings provide novel insight into the psychological mechanisms underpinning frequent consumption of LCS beverages in the context of their positive effect on weight, as
Acknowledgements
The research reported in this manuscript was funded by the American Beverage Association.
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