Nutrition. 2014 Sep;30(9):1007-10.

The liberating effect of weight loss supplements on dietary control: a field experiment.

Chang YY1, Chiou WB2.
  • 1Department of Hospitality Management, Tunghai University, Taichung, Taiwan, ROC and the Institute of Education, National Sun Yat-sen University, Kaohsiung, Taiwan, ROC.
  • 2Department of Hospitality Management, Tunghai University, Taichung, Taiwan, ROC and the Institute of Education, National Sun Yat-sen University, Kaohsiung, Taiwan, ROC. Electronic address:



Objectives: Taking weight-loss supplements may create illusion of protection against weight gain and thereby loosen subsequent dietary self-control. The current study examined whether taking weight-loss supplement would increase food intake and further tested whether positive attitudes toward supplements would increase susceptibility to overeating.

Methods: Participants were randomly assigned to take either a known placebo or a purported weight loss supplement (actually, the same placebo). After supplement provision, participants’ actual food consumption at a reward buffet lunch was recorded.

Results: Compared with controls, participants receiving a purported weight loss supplement ate more food at the reward buffet. Perceived progress toward the goal of weight reduction mediated the connection between use of weight loss supplements and subsequent food consumption. Participants
with more positive attitudes toward weight loss supplements were more susceptible to the liberating effect of taking weight loss supplements on food intake.

Conclusion: Using weight loss supplements may produce unintended consequences on dietary self-regulation. The public should pay more attention to the notion of psychological liberation when using weight loss supplements.

KEYWORDS: Dietary control; Liberating effect; Obesity; Weight loss supplements; Weight reduction

PMID: 24976417



Given that changes in diet and exercise habits are difficult to initiate and maintain, the use of weight-loss supplements has become an appealing alternative approach to weight management for obese patients and the public. Ironically, however, the obese population has increased at the same time as the use of weight-loss supplements has become widespread. In general, dietary choices are usually driven by multiple underlying goals. For instance, people may wish to fully enjoy culinary pleasure while maintaining a regime of weight reduction. According to the perspective articulated in the literature on progress toward multiple goals (1), actions used to infer progress toward one goal can liberate individuals and thereby increase their likelihood of pursuing incongruent actions. For example, Fishbach and Dhar (1) demonstrated that dieters who perceived greater progress toward their ideal weight were more likely to choose a tasty but fattening bar over a healthy snack. In a similar vein, taking weight-loss supplements may suggest that progress has been made and that the focal goal is nearly achieved. As a result, individuals may be more likely to pursue alternative goals.

Arguing from the notion of the liberating effect, we contend that engagement in actions such as taking weight-loss supplements, which can signal that sufficient progress toward weight reduction has already been achieved, may generate psychological liberation from subsequent dietary control. However, previous studies demonstrating the liberating effect were conducted in laboratory settings (1-3). To expand the generalizability of findings about psychological liberation, we examined the liberating effect of taking weight-loss supplements on dieting behavior in the context of a buffet-style reward meal. Moreover, the present study examined the moderating role of an attitudinal factor to test the boundary of the liberating effect. That is, we predicted that those users with more positive attitudes toward weight-loss supplements would experience more liberation and take greater advantage of supplement use by using it as evidence of their perceived progress toward weight reduction. We hypothesized that, if taking weight-loss supplements decreased dietary self-regulation, then such use would have an especially strong effect on users with more positive attitudes toward supplements.

Seventy female participants (mean = 28.16 years, SD = 5.69) who intended to lose weight were recruited to participate in the current experiment. This research focused on young adult women because a cross-sectional population-based survey showed that women aged 18–34 years were most likely to use supplements compared with other age by gender groups (4). Upon arrival, participants were asked to help a faculty member in the “Biology Department” with a functional food test to be used in a randomized, placebo-controlled study. They were randomly assigned to the weight-loss-supplement or the control group. Participants in the supplement group were told that, “The test pill will help you to attain weight loss,” whereas those in the control group were told that, “The test pill is a placebo that will be used in a future study.” Unbeknownst to participants, all received placebo pills. They then rated the perceived attributes of the pill they had just taken (e.g., size, shape, color, texture, and flavor) on a questionnaire that included an item measuring perceived progress toward their goal. The process of rating was a means of disguising the real purpose and gaining increased involvement from the participants. Participants were also asked to use a seven-point scale (1 = least likely, 7 = most likely) to indicate the extent to which they felt they were making progress toward the goal of weight reduction. After the manipulation, each participant was led to a student restaurant for a lunch buffet. The experiment occurred during six weekends, and each session involved 10–12 participants. The food in this buffet, which remained consistent over the course of the experiment, consisted of six healthy items (e.g., fruit, salad with Japanese dressing, vegetable pizza, steamed bean curd, steamed fish, and sugar-free green tea) and six less healthy items (e.g., chocolate cookies, French fries, fried chicken, cheeseburgers, soda, and custard). Each participant’s spontaneous food consumption was recorded by a yoked observer who followed and pretended to be a customer.

The results showed that participants who believed they were taking a weight-loss supplement ate a greater number of food items and consumed a greater number of less healthy items at a reward buffet. We also confirmed the mediating role of perceived progress toward the goal of weight reduction as a mechanism underlying the relationship between use of weight-loss supplements and subsequent poor dietary control (see Figure 1). Furthermore, this research showed that more positive attitudes toward weight-loss supplements were associated with increased susceptibility to the liberating effect.


Figure-11Figure. 1. Perceived progress toward the goal of weight reduction mediated the link between the use of weight-loss supplements and the number of food items eaten. The control condition was treated as the reference group (0 = placebo, 1 = weight-loss supplement) in mediation analysis. Numbers outside parentheses are unstandardized regression coefficients; numbers inside parentheses are the standard errors of regression coefficients. An asterisk indicates a P-value of less than 0.01. On the lower path, the values below and above the arrow are the results of analyses in which the mediator (perceived goal progress) was and was not included in the model, respectively.


The present findings demonstrated that weight-loss supplements may liberate users to loose the regulation of food consumption. People with intentions to lose weight appear to reward themselves for promoting their health in one domain (i.e., taking weight-loss supplements) by engaging in behaviors in a different domain (i.e., culinary delicacies) that conflict with the initial goal. These data differ from those showing liberating effects in same domain (1,3,5). This research contributes to our understanding of why the widespread use of weight-loss supplements does not appear to be correlated with successful weight reduction. We contend that “psychological” liberation may account for this interesting and important phenomenon. After taking weight-loss supplements, users may feel overly optimistic about their progress toward the goal of weight reduction and therefore begin to pursue culinary pleasure. Given that people generally are increasingly using supplements to lose weight, users should diligently monitor the liberating effect of taking weight-loss supplements on dietary control. In fact, psychological liberation may be avoided when weight-loss supplement users remind themselves of why they engage in weight-reduction behavior in the first place. If weight-loss supplement users can remember that their primary goal is weight reduction (i.e., goal commitment), the liberating effect may be attenuated or disappear altogether when they make subsequent diet-related choices. This insight may help translate the increased use of weight-loss supplements into successful weight reduction.


1. Fishbach A, Dhar R. 2005 Goals as excuses or guides: the liberating effect of perceived goal progress on choice. Journal of Consumer Research 32:370–377.
2. Wilcox K, Block L, Fitzsimons GJ, Vallen B. 2009 Vicarious goal fulfillment: when the mere presence of a healthy option leads to an ironically indulgent decision. Journal of Consumer Research 36:380–393.
3. Chang YY, Chiou WB. 2014 Taking weight-loss supplements may elicit liberation from dietary control: a laboratory experiment. Appetite 72:8–12.
4. Pillitteri JL, Shiffman S, Rohay JM, Harkins AM, Burton SL, Wadden TA. 2008 Use of dietary supplements for weight loss in the United States: results of a national survey. Obesity 16:790–796.
5. Finkelstein SR, Fishbach A. 2010 When healthy food makes you hungry. Journal of Consumer Research 37:357–367.

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