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A 16-week supplement study can’t accurately predict what a child’s weight gain will be in a year

Prebiotics reduce body fat in overweight children

Our Review Summary

This news release from the American Gastroenterological Association describes results of a clinical trial in 42 children with overweight or obesity and claims that a prebiotic powder that alters gut microbes can reduce body fat. It inappropriately claims that weight changes seen after four months will continue on the same trajectory for a full year, and only reports the weight differences that researchers predict will occur after a year — while omitting the actual results observed in the study after four months. That’s highly misleading.

Prebiotics are non-digestible food ingredients, including fiber. The prebiotics used in the study were oligofructose-enriched inulin. The intervention may have slowed the acquisition of body fat in some children, but the release doesn’t tell us how that benefit is related to alterations in gut microbes or why it would reduce future risk factors in adulthood.

The release acknowledges the need for a “larger clinical trial,” but the lede suggesting there may “soon” be a new tool in the fight against childhood obesity may be as far as some readers get.


Why This Matters

As the AGA release correctly points out, overweight in childhood tends to persist into adulthood and is an early risk factor for adult disease and death from obesity-related diseases. The study also is likely to be instantly newsworthy given the promise of an inexpensive dietary supplement that anyone can buy. The two quotes in the release — from an AGA advisory board member and one of the researchers, are appropriately cautious and a bit hyped, respectively. So the release could have been greatly strengthened if there had been more quantitative and qualitative information, and at least a nod to previous research and still unanswered questions about the safety, efficacy and use of prebiotic and probiotic products.


Does the news release adequately discuss the costs of the intervention?

Not Satisfactory

The release notes only that prebiotic supplements are “inexpensive.” A search of Amazon reveals a number of products with the same ingredients, in a wide range of costs.

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

To show a benefit, the release should have provided actual weight gain in each group, not the annual projected weight gain based on a 16-week study. According to the tables in the published study, both groups gained weight — as well as height. The treatment group gained 1.1 kg, and the placebo group gained 2.6 kg, a statistically significant finding.

The release would have been improved also with some context on what is the expected healthy range of weight gain in children 7 to 12 years olds and how much supplemental prebiotic was used.

Does the news release adequately explain/quantify the harms of the intervention?

Not Satisfactory

A quote indirectly suggests that the prebiotics are “non-invasive” but that doesn’t tell us a lot. Bloating and gas are often at least a temporary problem. It would have been useful to know how well children in the study tolerated the supplement.

And if the parents of children with obesity are not changing their diet (avoiding high fructose corn syrup, excessive prepared foods, and overfeeding), and letting the supplement do the work, that’s not teaching kids to eat healthily, which is an unintended consequence.

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

The release tells us that the study enrolled 42 children with greater than the 85th percentile of body mass index and that the study lasted 16 weeks, with daily dosing, but there was much more to the study that could have been easily included. The amount of supplement given to each child is a key omission. We’d also like to see more description on what in their microbiomes shifted, how rigorously those shifts were measured and how those shifts are thought to directly affect weight.

The release should have cautioned about the limitations of a short-term weight study. In most weight loss studies, initial rapid changes will gradually reverse with longer-term follow-up, and there’s no guarantee that weight in these children will follow the same trajectory observed after only 4 months.

Does the news release commit disease-mongering?


No disease mongering here; childhood obesity is widespread and a real threat to public health. The release would have benefited from inclusion of a note about the role of healthy diets, exercise and parent/child education in preventing childhood obesity as well as a caution that supplements may not be an antidote to poor adherence to a healthy lifestyle.

Does the news release compare the new approach with existing alternatives?

Not Satisfactory

The release didn’t mention any other alternatives for reducing childhood obesity such as diets, exercise and nutrition education. We also aren’t told whether any of the volunteers engaged in any of these alternative strategies during the time of the study and, if so, what impact they might have had on the results.

Does the news release establish the availability of the treatment/test/product/procedure?

Not Satisfactory

The release doesn’t address availability. The supplement used in the trial is from Germany and was not easy to find online, but as noted, similar products appear to be easily available.

Does the news release establish the true novelty of the approach?

Not Satisfactory

The release says this is the “first randomized controlled study to assess comprehensive changes” in gut microbial composition with prebiotics in overweight kids, but gives so little supporting information it’s hard to accept that claim. There have been other studies that cover at least some of the same territory in adults.

PubMed contains a number of studies (including those in adults) relating to prebiotics, gut microbiomes and weight loss, including some showing no difference from placebo.

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?


The language is mostly justifiable. A quote from the researcher calling the results “fantastic” is a bit over-the-top.

Total Score: 3 of 10 Satisfactory


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