It’s the end of the summer holidays – time for a DNA-based personalised diet and exercise plan?
Some people are more prone to weight gain than others and some people may find it harder to lose weight or exercise than others. These individual differences are undoubtedly at least partly influenced by genetics, but is there any evidence that a DNA-based personal diet or exercise plan will have added value over and above plans that do not involve a DNA test? Several online companies, including Direct-to-consumer (DTC) DNA testing companies would argue that they do and will charge you £99 or more for the test and the “personalised” advice. The websites are full of compelling arguments such as “One size does not fit all” and “one diet”, or one “Recommended Daily Dose” “does not suit all”. As academics competing for funding for more genetic research, it would be excellent news for us if such claims had merit because they would provide real world examples of useful applications of our research. However, after several interactions with some of the companies to find out which genetic variants they test and how that information is used, we have come to the conclusion that there is very little evidence that a genetic test will help you lose or maintain a healthy weight or diet or optimise your exercise regime. We simply dont know enough about the genetic variation involved in weight gain or loss or diet and exercise to “personalise” advice. Exceptions, often misleadingly cited by the online companies, include well known diet related diseases such as Celiac disease, lactose intolerance or PKU deficiency, where genetics play a strong role. PKU is a very rare inborn error of metabolism that is tested for at birth, so is irrelevant here, and we’d argue that gluten and lactose intolerance tests should be marketed as such, not to the general population as fitness and general diet advice where the implication is that the tests will benefit a large number of people.
For example, is there any evidence that people with a stronger genetic prediposition to obesity, such as that conferred by alleles in the
FTO gene, should diet or exercise differently to people with a weaker genetic predisposition? The answer is, currently no. Here is a review, written by scientists with similar expertise as ourselves, outlining why a DNA based test is highly unlikely to benefit you, whether you are trying to lose weight, “optimise” your diet, or are a professional cyclist. One telling statement in the abstract reads “Consequently, in the current state of knowledge, no… young athlete should be exposed to DTC genetic testing to define or alter training” Direct-to-consumer genetic testing for predicting sports performance and talent identification: Consensus statement. And here is another paper suggesting such testing is not currently useful: NIH Working Group Report—Using Genomic Information to Guide Weight Management: From Universal to Precision Treatment. Our conclusion is that, currently, when it comes to diet and exercise, one size does fit all – knowledge of the DNA sequences inherited from your parents wont help you.