“At-home microbiome tests improve weight-loss results by personalizing your diet.”
At-home microbiome tests have not been shown to improve weight loss beyond equally supported diet advice.
A stool test is not what makes a weight-loss plan work. When people got the same coaching, basing the diet on their gut microbes did not lead to more weight loss.
If you are weighing a microbiome test for weight loss, put that money toward coaching or a plan you can stick with instead.
In the trial that gave both groups the same coaching, a diet personalized partly from stool microbes did not beat a standard low-fat diet for weight loss. A company program using stool and blood tests led to a little more weight loss than general advice, but its comparison group got less support, so it cannot show the test itself helped; confidence is limited because there are only a few trials.
At-home microbiome tests have not been shown to improve weight loss beyond equally supported diet advice. In a trial where both groups got the same coaching, a diet personalized partly from stool microbes did no better than a low-fat diet.
The Personal Diet Study randomized 204 adults with obesity and prediabetes or type 2 diabetes. Both groups got 14 counseling sessions; one group also got meal scores from a computer program that used gut microbe data along with blood tests and other information. After six months, the personalized group had lost 3.3% of body weight and the low-fat group 4.3%, which was not a meaningful difference. In the ZOE METHOD trial of 347 adults, an 18-week app program built on stool, blood sugar and blood fat tests led to about 5.4 pounds more weight loss than general advice delivered through online resources, check-ins and a leaflet; the company funded the study and many authors worked for it. Because that program bundled several tests and the comparison group got less support, the result is about a different comparison and cannot show that the stool test itself added any weight loss. A 2025 international expert panel said evidence that microbiome tests are useful in medical care is scarce, and that direct-to-consumer tests have no proven value in practice.
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