A recent study shows knowing your genetic predispositions might actually end up putting you more at risk.

It’s no secret that genetic testing kits were one of the hottest holiday gifts this year, as Ancestry.com sold over 1.5 million on Black Friday alone. Besides tracing your family tree, these kits make some pretty big health claims, such as helping you determine your fertility and prevent chronic diseases based on your personal genetic makeup.

The latest claim being made by some genetic testing kit companies is understanding how your genetic predispositions can be an important tool for weight loss. 23andMe is now teaming up with artificial-intelligence coaching service, Lark Health, which delivers app-based weight loss and diabetes prevention advice based on your genetic information. While this sounds great in theory, critics say there’s not enough research to determine that diet should be based on your genetic makeup alone.

“The idea is good, but without the proof of peer-reviewed publications with prospective study, we have no knowledge whether these algorithms have any benefit,’’ Eric Topol, a geneticist at Scripps Research Institute, told Bloomberg.

Furthermore, a recent study published in Nature Human Behavior found that learning about your genetic dispositions may actually just become a self-fulfilling prophecy, rather than serving as a valuable tool for chronic disease prevention and weight loss.

Researchers from Stanford University advertised for participants interested in DNA-based diet and exercise plans, and genotyped 200 healthy adults. Participants were then split into two groups, with one taking a cardiorespiratory exercise capacity test, and the other taking a satiety test.

The participants chosen for the exercise test had to run on a treadmill for as long as they could, while researchers monitored their oxygen uptake and lung capacity. Those chosen for the satiety test had to consume a whole 480-calorie liquid shake, describe their level of fullness, and then receive a blood test for a satiety hormone. Individuals were then randomly assigned to receive either a “high-risk” or “protected” test result for obesity and repeated their respective test.

Findings showed some of those in the exercise group who had been randomly assigned a “high-risk” result for a gene variant associated with low endurance actually performed worse on their cardiorespiratory test the second time upon “learning” their results. These participants tired more easily and showed decreased oxygen uptake and lung capacity.

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The satiety group also had many of its participants who received a “high-risk” result report skewed results after taking their test the second time. Even after being given the same liquid meal, participants who had been told they possessed an appetite-suppressing gene variant reported feeling fuller than before. Participants were told their actual genetic results at the end of the study.

The study noted that effects of perceived genetic risk on outcomes were sometimes greater than the actual effects associated with genetic risks of these two variants.

“If simply conveying genetic risk information can alter actual risk, clinicians and ethicists should wrestle with appropriate thresholds for when revealing genetic risk is warranted,” the authors of the study warned.

Clearly, there is still much more research needed before we can truly trust our genetics as a weight loss compass. Until then, there is plenty of research on how regular exercise, a healthy diet, and simply just getting enough sleep can all lead to lasting weight loss and chronic disease prevention.