Expectancy, Self-Efficacy, and Placebo Effect of a Sham Supplement for Weight Loss in Obese Adults

Abstract

This study examined the role of expectancy in the placebo effect of a sham dietary supplement for weight loss in 114 obese adults. All participants received lifestyle education and were randomized to one of three conditions: 1) a daily placebo capsule and told that they were taking an active weight loss supplement; 2) daily placebo and told they had a 50% random chance of receiving either the active or placebo; or 3) no capsules. At 12 weeks, weight loss and metabolic outcomes were similar among the three groups. Participants in both groups that took capsules showed decreased weight loss self-efficacy and increased expectations of benefit from dietary supplements. Participants not taking capsules showed the opposite. Adverse events were more frequently reported in groups taking capsules than those who were not. These findings suggest that supplements without weight loss effects may have nocebo effects through diminished self-efficacy.

Placebo effects on the quantity and quality of relaxation training

“…Moreover, it has been shown that placebos can even negatively affect the motivation and effort to show a specific behavior. For example, Tippens et al (2014) found that participants with stronger beliefs in a placebo (100% expectation to have received a dietary supplement for weight loss) reported a decline in self-efficacy throughout the study and tended to lose a smaller proportion of weight than participants with less pronounced beliefs. Similar findings have been reported by Höfler et al (2019).…”

Cognitive remediation for individuals with psychosis: efficacy and mechanisms of treatment effects

“…While there is evidence that trial quality does not affect the relationship between CR and cognitive or functional change (Wykes et al 2011), it is nevertheless important to point out that without an active control group, there is no way for us to determine to what degree, if any, non-specific effects of CR and/or staff contact may have contributed to the cognitive and functional improvements in the CR group. The enhanced structure of attending a CR program, the corresponding social interactions while at the hospital with staff and other patients, and the perception that the person is doing something active for his or her mental or physical health may all influence cognition and quality of life, and especially those aspects related to motivation for treatment and self-efficacy (Boot et al 2013; Tippens et al 2014; Schwartz & Buchel, 2015). This is particularly relevant to our findings since the only subdomain of the QLS that improved during CR was the intrapsychic foundation subscale, from which several items have been commonly used in schizophrenia research to measure an overall state of motivation (Nakagami et al 2008).…”

Unsolved, Forgotten, and Ignored Features of the Placebo Response in Medicine

“…For example, expectation of a high-versus low-fat drink significantly affected symptom scores, irrespective of the actual fat content of the (yogurt) meal, 58,59 a neurocognitive phenomenon which has been called "mindset" recently in this context 60 according to a person's set of associations and attitudes that shape respective expectations and behaviors. In another study with healthy volunteers information to have received a nutrient supplement facilitating weight loss increased the belief in the supplement over the course of the study, 61 although it decreased the person's selfefficacy toward weight control. Similarly, information about the potential health benefits of bodily work (room cleaning) resulted in beneficial health outcomes (decrease in blood pressure, body mass index, etc.)…”