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

Abstract

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...

Registration status and methodological reporting of randomized controlled trials in obesity research: A review

“…Our findings showed that the proportion of registered RCTs in obesity journals slightly exceeds values of RCT registration in major medical journals and far surpasses values reported previously in the fields of clinical psychology and oral health . This suggests that the registration status of obesity RCTs is relatively optimal compared to other fields, which may be reflective of recent calls for improved methodological rigor in the field of obesity research , an observation that is consistent with our finding regarding increased prospective registration status in more recent years. It is noteworthy that the proportion of registered RCTs did not differ by the degree to which journals' authorship guidelines were explicit, a finding echoed by others , indicating that existing authorship guidelines, editorial screening processes, and peer‐reviewing procedures may not effectively ensure adherence to registration and reporting requirements.…”

“…In the field of obesity research, experts have long advocated for increased attention to the conduct and methodological reporting of trials . Recently, there have been calls to improve methodological rigor in obesity research , enhancements that are vital to ensure that the highest‐quality evidence possible is generated to inform decision‐making for preventing and managing obesity. High‐prevalence estimates of obesity in Canadian children and adults underscore the need for rigorously designed trials to determine the efficacy and effectiveness of strategies that are designed to prevent and manage obesity; in turn, this information can form the scientific basis for making policy‐related decisions and allocation of resources across multiple jurisdictions (e.g., municipalities, health care and school systems, industry) that can influence our weight and health.…”

How fragile are Mediterranean diet interventions? A research-on-research study of randomised controlled trials

“…9 10 Apart from many 'followers' however, several scientists are also questioning the MD. Some are high-lightening the observational design of the Seven Countries study, 11 while others are stressing the limitations of nutritional epidemiology in general, 12 often incorporating selective reporting, 13 inflated results, 14 over-interpretation and skewed perspectives, 15 with large flexibility in the performed analyses which can be based οn questionnaires of low reproducibility. 16 Subsequently, research designs were improved to minimise bias, 14 and the focus shifted to randomised controlled trials (RCTs), situated higher in the pyramid of evidence.…”

Scientific rigor and credibility in the nutrition research landscape

“…Various fields and parties have expressed such concerns and put forth efforts to strengthen the integrity of the scientific process, such as the American Statistical Association (6), the Center for Open Science (7), individual universities [e.g., (8)], and government funding agencies [e.g., (9,10)]. Similar concerns and efforts are evident in nutrition and obesity research (11)(12)(13) as areas of scientific work in which the importance of trust appears especially salient (14)(15)(16)(17)(18).…”