It's just that it doesn't seem to happen.
My friend Tim Caulfield has written about this extensively, including in this piece last year in The Atlantic, and now another study has come out to add to the pile of disappointments.
Published in PLoS in late November, the study looked at whether or not randomly assigning patients to receive genetic and phenotypic risk assessments regarding their potential future development of type 2 diabetes would change their behaviours as compared to those randomized to receive general advice.
What they found wasn't exciting. The addition of genetic testing information to lifestyle advice did nothing to increase physical activity, diet, weight, worry, or anxiety in the short term in those tested.
And while the researchers described the short duration of follow up as a weakness (it was 8 weeks), I think it might just as easily be describable as a strength in that one could argue that a person would be most likely to affect change while the iron of new information was hot, and that here, where no changes were observed immediately post risk provision, is more damning than would be demonstrating that changes dissipate with time.
From a clinical perspective, the other question that needs to be answered is whether or not the degree of change, if there were change, consequent to the inclusion of genetic testing to personalized, but not genetically informed, nutrition advice, would be superior? Putting this another way, if genetic testing affected change, would the changes it inspired be of greater clinical benefit than would healthy living advice provided by RDs and tailored, non-genetically, but certainly individually, to the person sitting in front of them?
And it would seem that's a fair thought given this quote by the founder and chief science officer of a company selling these sorts of nutrition related genetic tests who told the Wall Street Journal,
"For people who already eat a healthy diet, nutritional genetic testing might not be that useful"All this to say, if you're keen for change, and if you have the money to spend on improving your health and diet, and unless you can afford both and that you also recognize these are very early days for nutritional genomics, save your blood and hire an RD to work with you on broader changes geared to help you find your way to a healthy diet.
(Disclosure: Though we could, our office doesn't offer nutritional genetic testing, but we do offer RD counselling)
[And if you're interested in another take on this industry, here's the piece Julia Belluz published about it yesterday]