Interest in vinegar as a health remedy is perennial. Apple cider vinegar (ACV) is simply vinegar made from fermented apple cider. Chemically, it is mostly dilute acetic acid, the same ingredient found in ordinary white vinegar. In 2024, a study published in BMJ Nutrition, Prevention & Health reported that a small daily dose of apple cider vinegar produced dramatic weight loss 6–8 kilograms (13-17 pounds) over 12 weeks. The paper was withdrawn more than a year later after substantial criticism. But even before concerns about methodology and reporting were raised, the magnitude of the results should have prompted skepticism: The numbers reported did not align with basic physiology.
The Study and its findings
The trial, entitled Apple cider vinegar for weight management in Lebanese adolescents and young adults with overweight and obesity: a randomised, double-blind, placebo-controlled study was published in January 2024. The study population included 120 participants aged 12-25 years (with a body mass index (BMI) of 27-34.5 kg/m²). Participants were divided into three groups who took 5mL, 10mL, or 15mL daily ACV diluted in 250mL water, versus a placebo control, over 12 weeks. Participants were instructed to maintain their usual diets (and track in a diary) without additional interventions. Measurements of weight, BMI, waist/hip ratios, and blood markers like fasting glucose, triglycerides, and cholesterol were taken at baseline and weeks 4, 8, and 12.
The authors reported that all ACV groups showed significant reductions in weight (up to 6-8kg in the 15mL group by week 12), BMI (decrease by an average of 2.7 to 3.0), body fat ratio, and metabolic parameters compared to baseline and placebo. The authors concluded that ACV consumption improved anthropometric and metabolic outcomes, potentially supporting its use as a dietary intervention for obesity management.
The Energy Math
Even a cursory read of the study will likely prompt questions, but let’s take the findings at face value based on what was reported. The group with the largest reported weight loss consumed 1 tablespoon (15mL) apple cider vinegar (5%) daily. That’s 0.75mL of acetic acid. That’s about 15 drops of liquid.
Now look at the reported results:
- 1 kg of fat stores approximately 7000-7,700 kcal
- 6-8 kg represents 45,000 – 60,000 kcal
Over 12 weeks, this implies a sustained calorie deficit of 500-700 kcal per day.
A 500 kcal daily deficit is the result of a major change in lifestyle. It means eating substantially less, every day. Or you could burn it by running 30-45 minutes at 10km/hour. Walking briskly, it would take 60-90+ minutes to burn this many calories.
There is no known mechanism by which a small amount of a common food product can increase one’s metabolic rate by 500–700 kcal per day, sustained for three months. We would expect obvious increases in heat production, heart rate, and other systemic effects. People would feel it. Clinicians would identify it. It would not be difficult to distinguish the treatment group from the placebo.
So if the scale is moving by 6–8 kg over 12 weeks, but there is no corresponding change in physiology or behavior, the claim lacks face validity. Either intake was reduced in ways not accounted for, weight was mismeasured, or the study design failed. What it cannot plausibly represent is a dramatic metabolic effect of a widely consumed kitchen ingredient.
But that’s not all
The implausibility of the effect size naturally led readers to examine the study more closely. And once scrutiny began, substantial problems were identified.
Without even looking at the trial, critics noted it had not been registered in advance. The reporting itself didn’t follow expected standards for randomized controlled trials – standards that were supposed to be a journal standard.
Critics noted improbabilities in the reported data, including discrepancies in baseline characteristics and outcome reporting. Questions were raised about the randomization process, the adequacy of blinding, and whether dietary intake and physical activity were sufficiently controlled or monitored. Given that weight loss of this magnitude would almost certainly require reduced energy intake, the absence of any analysis of dietary intake, despite participants keeping diaries, was surprising.
There were also concerns about statistical reporting and the internal coherence of the results. When effect sizes are large but the surrounding methodological details are limited, questions are to be expected. While the authors stated “All data relevant to the study are included in the article or uploaded as supplementary information,” none was available.
One critic noted that the results suggested that ACV was far more effective than semaglutide (Ozempic) which results in a 6% weight loss at 12 weeks – less than up to 9% found with ACV. That critic noted,
An unpatentable, freely available, absolutely harmless dietary intervention that is 50% more effective at short/medium term weight loss than GLP-1 agonists for ~1/1000th of the price feels improbable.
Ultimately, the journal withdrew the paper. Retractions are part of science’s self-correcting process. But in this case, the warning signs should have been visible during the peer review process: the results did not make physiological sense.
Spotting bad data
Retractions reflect the self-correcting nature of science. But the key point I wanted to make by blogging about a retraction is not that the process works. It is about how the reader needs to consider these types of studies.
When evaluating claims about weight loss, especially those involving common foods or supplements, start with the size of the reported effect. Large, sustained weight changes require large, sustained shifts in energy balance. Those shifts must come from either reduced intake, increased expenditure, or pharmacologic effects that meaningfully alter appetite or metabolism. These are the only ways you can change energy balance.
If a study reports dramatic weight loss from a simple intervention, ask these questions:
- What daily calorie deficit would this result require?
- What mechanism could plausibly produce that deficit?
- Would that mechanism produce noticeable physiological effects?
If the answers are unclear, implausible, or absent, it’s reasonable to be skeptical of the findings. And where the findings are an outlier, or are called “unprecedented”? Even more skepticism is warranted.
The appeal of simple solutions is understandable. A tablespoon of vinegar is inexpensive, accessible, and harmless in small amounts. But physiology has no regard for these factors. Energy balance is not suspended because an intervention is “natural.” This shouldn’t have passed peer review – and until all the discrepancies are actually addressed, it’s reasonable to keep thinking of ACV as a food and not a miracle weight loss cure.