This study of 120 individuals that were above a healthy weight, aged between 12 and 25 years old, who were provided with either 5ml which is about a teaspoon, 10ml or 15ml of apple cider vinegar per day, one group were given a placebo drink which did not contain any apple cider vinegar. Subjects were asked not to alter their diet or exercise patterns over the 12-week period.

The weight loss experienced by all those who received the apple cider vinegar was remarkable, about 6kg over 12 weeks, when compared to the group who did not take any apple cider vinegar, who only lost only a tiny amount of weight. The authors conclude that weight loss and improvements in metabolic markers were due entirely to the apple cider vinegar. Although this study design has the ability to prove cause and effect there are some substantial problems in this study, which would make the conclusions drawn questionable.

First, the subjects were not weight stable at the beginning of the study, so may have been on a weight loss journey before they began taking the vinegar, diet and activity were self-reported so we cannot be sure that these large weight losses were not due to lifestyle changes, plus the use of weight loss medications has not been reported.

There is existing evidence that weight loss of around [more than] >5% body weight, which was achieved in this study, leads to improvements in risk factors for heart disease itself.  Here the authors suggest that these are solely due to the apple cider vinegar and have not taken into consideration the actual weight changes.

The results reported here are remarkable but would need to be reproduced in a more rigorously controlled environment before any confidence could be placed in their conclusions. It would be wonderful if a teaspoon of apple cider vinegar caused substantial weight loss, but with the complexity of obesity and its management that we grapple with, sometimes if something seems too good to be true - it often is.

Recent research has investigated the health effects of apple cider vinegar. Researchers tested the impact of daily apple cider vinegar consumption in 120 overweight and obese adults over 12 weeks.
 
While findings showed apple cider vinegar may offer some benefits for weight loss and for lowering blood sugar, cholesterol, and triglycerides, it is unlikely to be a silver bullet for health.
 
One missing piece from this study is how participants' diets influenced the outcomes. While participants kept diet diaries, specific details on calorie and/or macronutrient intake were not reported in the study. Ideally, all outcomes would have accounted for dietary intakes, especially given 7% of participants were on a diet at baseline.
 
This study was also small with 120 people, short in duration and only focused on young and overweight individuals. We can’t extrapolate the findings to the broader population or draw conclusions about the long-term efficacy of apple cider vinegar.  Also while included participants reported no side effects in the short term, they did exclude individuals who experienced heartburn from the vinegar. It is important to consider potential longer-term side effects of apple cider vinegar such as the impact of its acidic nature on dental health.
 
While apple cider vinegar may offer some short-term health benefits, particularly for young and overweight individuals, it should not be viewed as a solution to Australia’s obesity epidemic.

The problems I see with this paper are that these were young people with an average age of 17 ± 5 years. That means some were as young as 12. Some may have still been growing and this would affect their weight. We are also told that "Subjects consumed their normal diets throughout the study. The contents of daily meals and snacks were recorded in a diet diary" but no details are given so we have no idea whether some may have been consuming less - or changed the amount they were eating during the study.

The average weights given for each group are similar but the confidence intervals are so high that we can't assign any real statistical significance. Some references come from journals that would be considered as low ranking for scientific accuracy (eg Journal of Functional Foods). I don't have access to this journal so I can't assess the findings of the study quoted but the brief notes say 39 subjects and no 'blinding'. They also followed a low-calorie diet (no details). Another study cited as backing for the BMJ group's findings was a 2009 study in a Japanese group using vinegar but not apple cider vinegar. The results given do not accord with claims the vinegar group lost weight - again, the confidence intervals in the before and after weight values discount statistical significance.

Another concern is that there is no data on dental effects. A number of studies show the erosive effect on vinegar on dental enamel.

There were small falls in total cholesterol and that has also been shown in several other studies.

There are several repeated measures over time, but they don't use the proper statistical methodology for repeated measures in a longitudinal design of this type.

They only apparently use t-tests (a statistical tool for making comparisons) and they should have used other models that allow for the valuation of fixed and random components.  They also don't describe the total diet of the participants and how their caloric intake changes, the consumption of fruits, vegetables, ultra-processed foods, and so on.

In short, this needs caution, a lot of caution.

The paper describes the effect of taking different amounts of apple cider vinegar daily on body weight and adiposity in young adults, versus a placebo.  Subjects were randomised into four groups.

The authors claim beneficial effects of the vinegar on a range of measures including body weight, BMI and waist circumference, as well as blood lipids but it is concerning that the data were analysed by Student’s t tests with no correction for multiple comparisons. 

Moreover, effects over time would normally require repeated measure statistical analysis. 

Subjects were reported to have eaten their normal diet over the study, but it is unclear what tool was used to assess this.  While a number of effects of acetic acid on the expression of genes involved in fatty acid oxidation have been reported in animal studies, the mechanism of any effect observed here is unclear.

This paper has shown in a double-blinded randomised controlled trial, that apple cider vinegar consumption could aid in weight loss. A small number of participants (30 in each group) were instructed to consume either 5, 10 or 15 ml of apple cider vinegar each morning before they ate. Over a period of 3 months apple cider vinegar consumption was associated with significant falls in body weight and body mass index (BMI).  On average, those who drank apple cider vinegar once daily during that period lost 6–8 kg in weight and reduced their BMI by 2.7–3 points, depending on the dose. The authors also reported decreases in levels of blood glucose, triglycerides, and cholesterol. The placebo group who were given water with lactic acid had much less weight loss and no changes to blood glucose levels or blood lipids.

This study is promising however there are some concerns. This study was undertaken in people between the ages of 12-25 years, so the results can not be generalised to everyone. Additionally, from the statistical analyses that were done we can’t be confident that everyone who tried this would lose this average amount of weight.

While they kept records of the participants' diet and exercise this was not published in the paper, which makes it more difficult to determine if the diet or exercise might have had an impact. For example, did they change the amount they ate or the types of food they ate? Another concern is that even though participants were blinded to the treatment they received, the researchers did not check afterwards whether the participants guessed correctly which group they were in. Furthermore, the authors did not report if anyone dropped out of the study.

This study provides some good evidence for future larger and longer studies to be conducted across a range of ages to provide more robust evidence to see if apple cider vinegar could be a useful aid for weight loss.