Tag: weight-loss

The authors, the wellness industry, and the journal publisher BMJ Group have been set back after they retracted a widely publicized study that helped fuel the rise of the apple cider vinegar (ACV) trend. Researchers found that the study, which suggested that consuming one to two teaspoons of ACV daily could lead to significant weight loss and metabolic benefits, contained ‘multiple errors’ and unverifiable results.

After growing concerns over the frequently cited study—ranging from journal letters to a formal review by BMJ’s content integrity team and independent statisticians—experts were unable to replicate its dramatic findings. They identified “implausible statistical values,” unreliable raw data, poor reporting practices, and the absence of prior trial registration. The authors consented to the retraction, attributing the issues to honest mistakes.

A journal spokesperson stated that the journal is retracting the paper because the authors couldn’t replicate their analyses and researchers found multiple errors. “The dataset provided by the authors also showed patterns inconsistent with random participant assignment and improbably small p-values, considering the limited sample size used in the study.”

Study Retraction Sparks Caution Despite Promising Weight-Loss Claims

Although the journal BMJ Nutrition, Prevention & Health removed the published study, a March 2024 news release release still presents its details. The study, a three-month trial examining ACV’s weight-loss effects, involved 120 participants assigned various daily dosages. According to the authors, participants experienced an average weight loss of 6–8 kg (13–17.6 lbs) and a BMI reduction of 2.7–3 points. Despite acknowledging certain limitations, the study’s striking results gained significant media attention.

At the time of the study’s publication, BMJ Nutrition, Prevention & Health co-owner Shane McAuliffe noted that while the intervention showed promise in terms of feasibility and effectiveness—potentially paving the way for future trials exploring broader applications—he urged caution in interpreting the findings. He emphasized that researchers should not generalize conclusions about apple cider vinegar’s independent effects, and he urged them to conduct further studies with more detailed dietary reporting to address possible confounding factors. Future studies, he added, should explore how ACV affects biochemical markers like lipids and blood glucose, beyond just weight loss.

Editor-in-chief Professor Martin Kohlmeier also admitted that the journal made a mistake by publishing a trial that the authors hadn’t prospectively registered, clearly violating its policies.

Reflecting on Publication Decisions and Challenges in Nutrition Research

“In retrospect, this was the wrong call,” he said. “However, the authors are from a scientific community that is underrepresented in nutrition research. The journal seeks to promote strong evidence, typically from clinical trials—though these are rare in nutrition science due to the complexity, scale, and time required to conduct them.”

Because of the challenges involved in conducting clinical trials, nutrition research often relies on observational studies that draw from large datasets like the UK Biobank—allowing only for the identification of correlations, not causal relationships.

Dr. Helen Macdonald, Publication Ethics and Content Integrity Editor at BMJ Group, stated:
“While it may be tempting to promote what appears to be a simple and effective weight-loss solution, the study’s findings are currently unreliable. Journalists and others should stop referencing or using this study in any future reporting.”

Replication Failure and Expert Criticism Raise Doubts About Study’s Validity

A major concern with the study was the inability to replicate its results. Scientists consider replication a vital—though sometimes neglected—part of research, as it helps confirm the reliability of original findings. While replication failures can result from factors like human error, poorly documented methodologies, or other hard-to-control variables, the inability to verify results raises serious concerns about a study’s credibility.

In this case, independent experts raised concerns about the study’s data collection methods, lack of transparency, and the age of participants.

Dr. Rosemary Stanton OAM, a nutritionist and Senior Visiting Fellow at the University of New South Wales, pointed out:
“One major issue is that the participants had an average age of 17 ± 5 years—meaning some were as young as 12. Some of them may still have been growing, which could naturally influence their weight. The study also claims that participants maintained their usual diets and logged their meals in a food diary, but no specific details were provided. Without that information, it’s impossible to know if participants ate less or changed their eating habits during the trial.”

Concerns Over Participant Stability and Flawed Statistical Analysis

Professor Helen Truby from The University of Queensland echoed these concerns, adding:
“The participants weren’t weight-stable at the beginning, which suggests some may have already been trying to lose weight before starting the vinegar regimen. Because participants self-reported both their diet and physical activity, researchers can’t determine whether ACV or lifestyle changes actually caused the reported weight loss. Additionally, there’s no information on whether any participants were using weight-loss medications.”

Additional experts criticized the way the researchers analyzed their results, arguing that the statistical approach used did not adequately reflect the complexity of the data.

“They appear to have relied solely on t-tests, which are basic tools for comparison, but they should have applied more advanced models capable of evaluating both fixed and random effects,” explained Miguel Ángel Martínez González, Professor of Preventive Medicine and Public Health at the University of Navarra. Because participants self-reported both their diet and physical activity, researchers can’t determine whether ACV or lifestyle changes actually caused the reported weight loss. Furthermore, the researchers failed to detail the participants’ overall diets, including changes in calorie intake, or the consumption of fruits, vegetables, and ultra-processed foods.”

Study Limitations and Ongoing Debate Over Apple Cider Vinegar’s Weight Loss Effects

Dr. Evangeline Mantzioris, Program Director of Nutrition and Food Sciences at the University of South Australia, noted the study’s potential but highlighted key flaws: it involved only 12 to 25-year-olds, limiting broader applicability, and the statistical analysis didn’t guarantee consistent weight loss for all. Researchers tracked diet and exercise but didn’t report them, making it unclear whether lifestyle changes influenced the results. Additionally, the study didn’t verify if participants knew their treatment group or report any dropouts.

While this particular study has been discredited mainly due to poor methodology and lack of detail, apple cider vinegar has been the subject of other research. A 2009 Japanese study first sparked interest by suggesting ACV might lead to modest weight loss. In the years since, many researchers—including the authors of the now-retracted paper—have attempted to replicate those findings. However, the overall evidence remains inconclusive, and no studies to date support the dramatic 6–8 kg (13–17.6 lb) weight loss claimed by the withdrawn research.

Furthermore, as outlined in a 2014 review, scientists continue to disagree on how exactly apple cider vinegar affects glucose and lipid metabolism.

Limited Evidence on Health Benefits Amidst Growing Apple Cider Vinegar Market

“While there is some evidence suggesting vinegar may be a helpful complementary treatment for individuals with glucose and lipid disorders, more extensive, long-term studies with rigorous methodology are needed before any conclusive health claims can be made,” the researchers stated.

Despite the controversy, the global apple cider vinegar (ACV) market is now worth over US$1 billion (as of 2023–2024) and continues to expand—suggesting that the retraction of a single study is unlikely to slow its momentum.

“Although some evidence indicates that apple cider vinegar might support weight loss and help reduce blood sugar, cholesterol, and triglyceride levels, it’s unlikely to be a miracle solution for overall health,” said Dr. Daisy Coyle, an Accredited Practising Dietitian at The George Institute for Global Health.

“Although several animal studies have shown that acetic acid can influence the expression of genes related to fatty acid oxidation, the exact mechanism behind any effects seen in this study remains unclear,” said Margaret Morris, Professor of Pharmacology and Head of the Environmental Determinants of Obesity Group at the University of New South Wales. “This research offers promising groundwork for future, larger-scale and longer-term studies involving diverse age groups to gather stronger evidence on whether apple cider vinegar could be an effective weight-loss aid.”

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Read the original article on: New Atlas

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