Placebo effects in obesity research

Fontaine, Kevin R.; Williams, Michelle; Hoenemeyer, Teri; Kaptchuk, Ted J.; Dutton, Gareth R.

doi:10.1002/oby.21456

Cited by 20 publications

(22 citation statements)

References 12 publications

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“…Another limitation of the study could be the use of a natural history control group (no treatment) instead of a null control group receiving placebo drops. It has been documented that participants randomised to placebo-control conditions in obesity research studies often report improved outcomes that are similar to those of people receiving the active treatment, even when the individual is aware that they are receiving a placebo [ 57 , 58 ]. A control for sweetness could be another NNS arm, such as saccharin, aspartame, sucralose, etc., but that was out of the scope of this trial at this time.…”

Section: Discussionmentioning

confidence: 99%

Effects of the Daily Consumption of Stevia on Glucose Homeostasis, Body Weight, and Energy Intake: A Randomised Open-Label 12-Week Trial in Healthy Adults

et al. 2020

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Stevia is a non-nutritive sweetener, providing sweet taste with no calories. This randomised, controlled, open-label 2-parallel arm trial examined the effects of daily stevia consumption on glycaemia in healthy adults. Secondary endpoints included body weight (BW) and energy intake (EI). Healthy participants (n = 28; aged 25 ± 5y, body mass index 21.2 ± 1.7 kg/m2) were randomised into either the stevia group (n = 14)—required to consume a stevia extract daily—or to the control group (n = 14). At weeks 0 and 12, the glucose and insulin responses to an oral glucose tolerance test were measured; BW and EI were assessed at weeks 0, 6, and 12. There was no significant difference in the glucose or insulin responses. There was a significant main effect of group on BW change (F(1,26) = 5.56, p = 0.026), as the stevia group maintained their weight as opposed to the control group (mean weight change at week 12: −0.22 kg, 95%CI [−0.96, 0.51] stevia group, +0.89 kg, 95%CI [0.16, 1.63] control group). The energy intake was significantly decreased between week 0 and 12 in the stevia group (p = 0.003), however no change was found in the control group (p = 0.973). Although not placebo-controlled, these results suggest that daily stevia consumption does not affect glycaemia in healthy individuals, but could aid in weight maintenance and the moderation of EI.

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Section: Discussionmentioning

confidence: 99%

Effects of the Daily Consumption of Stevia on Glucose Homeostasis, Body Weight, and Energy Intake: A Randomised Open-Label 12-Week Trial in Healthy Adults

et al. 2020

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“…It is interesting that depressive symptoms improved over the waitlist period, suggesting that changes may occur in adolescents’ psychological symptoms if they perceive impending availability of support. Fontaine et al [ 50 ] suggest that intervention outcomes may be influenced via placebo-related factors such as expectations of improvement, interaction with staff, and desires of improvement. Indeed, in psychotherapy settings where participant expectations have been extensively studied, researchers have noted the importance of considering the impact of expectations on participant outcomes following intervention [ 51 , 52 ].…”

Section: Discussionmentioning

confidence: 99%

Relationships between psychosocial outcomes in adolescents who are obese and their parents during a multi-disciplinary family-based healthy lifestyle intervention: One-year follow-up of a waitlist controlled trial (Curtin University’s Activity, Food and Attitudes Program)

Fenner

Howie

Davis

et al. 2016

Health Qual Life Outcomes

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BackgroundLimited studies have investigated relationships in psychosocial outcomes between adolescents who are obese and their parents and how psychosocial outcomes change during participation in a physical activity and healthy eating intervention. This study examined both adolescent and parent psychosocial outcomes while participating in a one - year multi-disciplinary family-based intervention: Curtin University’s Activity, Food, and Attitudes Program (CAFAP).MethodsFollowing a waitlist control period, the intervention was delivered to adolescent (n = 56, ages 11–16) and parent participants over 8 weeks, with one-year maintenance follow-up. Adolescent depression and quality of life, family functioning, and parent depression, anxiety, and stress were assessed at six time points: baseline and prior to intervention (e.g., waitlist control period), immediately following intervention, and at 3, 6, and 12 months post-intervention. Relationships between adolescent and parent psychosocial outcomes were assessed using Spearman correlations and changes in both adolescent and parent outcomes were assessed using linear mixed models. Changes in adolescent psychosocial outcomes were compared to changes in behavioural (physical activity and healthy eating) and physical (weight) outcomes using independent samples t-tests.ResultsThe majority of psychosocial outcomes were significantly correlated between adolescents and parents across the one-year follow-up. Adolescent depression, psychosocial and physical quality of life outcomes significantly improved before or following intervention and were maintained at 6-months or one-year follow-up. Parent symptoms of depression, anxiety, and stress were reduced during waitlist and primarily remained improved. Changes in adolescent psychosocial outcomes were shown to be partially associated with behavioural changes and independent of physical changes.ConclusionsAdolescents in CAFAP improved psychosocial and physical quality of life and reversed the typical trajectory of depressive symptoms in adolescents who are obese during a one-year maintenance period. CAFAP was also effective at maintaining reductions in parent symptoms of depression, anxiety, and stress demonstrated during the waitlist period.Trial RegistrationThe trial was registered with the Australian and New Zealand Clinical Trials Registry (No. 12611001187932).

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“…Three insightful papers in this issue (1)(2)(3) highlight different types of biases and errors in obesity research and related fields of investigation. George et al (1) review a wide variety of errors and biases in misuse of statistical methods, misconceptions in scientific inference, improper or inadequate consideration of multiplicity, and suboptimal or selective reporting.…”

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confidence: 99%

Biases in obesity research: Identify, correct, endorse, or abandon effort?

Ioannidis

2016

Obesity

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Three insightful papers in this issue (1-3) highlight different types of biases and errors in obesity research and related fields of investigation. George et al.(1) review a wide variety of errors and biases in misuse of statistical methods, misconceptions in scientific inference, improper or inadequate consideration of multiplicity, and suboptimal or selective reporting. Johns et al. (2) provide a metaepidemiological assessment of data from control groups from 29 randomized trials of obesity and show that participants in inactive control groups spuriously seem to lose weight after 12 months-an extra reason why non-controlled studies should be less trusted. Fontaine et al. (3) discuss the subtleties of placebo effects and how placebo-related factors may cause an effect even among people who know that they are receiving a placebo.Errors and biases are by no means unique to obesity research. They pervade all fields of scientific investigation (4). However, obesity and related fields, in particular nutrition research, have received an extra share of attention on these issues. There are probably many reasons for this, including the unquestionable importance of the subject matter; the extra interest for this topic (especially the "bad news") by mass media (5); the refutations of scores of epidemiological associations especially in nutrition research (6); the large volume of papers published; the persistence of some myths based on no evidence (7,8) which distort further investigation by offering a wrong starting point; the routine use of measurement tools with high error rates and serious biases (e.g., nutrition questionnaires based on selfreporting) (9); the relative lack of transparency (e.g., no prespecified protocols, registration, data sharing); and the recalcitrance of some segments of this literature to adopt standard practices (e.g., proper adjustment for multiple comparisons and more stringent statistical thresholds) that might have saved several embarrassments.Some fields in observational research in particular have seen the massive propagation of the practice of "salami slicing," where dozens of investigators co-author papers practically reporting a single association at a time and where each paper consists of a tiny part of a much larger data dredging agenda from the same data set "gold mine." In observational research, some data sets have already published hundreds of papers (10) instead of a couple dozen that would have been more appropriate, e.g., if they had used exposure-wide association approaches that can evaluate dozens and hundreds of exposures within the same analysis (11,12). Salami slicing is also seen increasingly in some randomized trials of nutrition and obesity, where multiple publications of outcomes and analyses stem from the same trial. For example, a search in PubMed (December 17, 2015) with PREDIMED [ti] or "PREDIMED Study Investigators" retrieves 95 papers. Even though this is an excellent, pivotal randomized trial, one can question how much data dredging a single trial can tolerat...

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Placebo effects in obesity research

Cited by 20 publications

References 12 publications

Effects of the Daily Consumption of Stevia on Glucose Homeostasis, Body Weight, and Energy Intake: A Randomised Open-Label 12-Week Trial in Healthy Adults

Effects of the Daily Consumption of Stevia on Glucose Homeostasis, Body Weight, and Energy Intake: A Randomised Open-Label 12-Week Trial in Healthy Adults

Relationships between psychosocial outcomes in adolescents who are obese and their parents during a multi-disciplinary family-based healthy lifestyle intervention: One-year follow-up of a waitlist controlled trial (Curtin University’s Activity, Food and Attitudes Program)

Biases in obesity research: Identify, correct, endorse, or abandon effort?

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