Would a DNA test help you stick to your diet?


Imagine if your body came with an instruction manual explaining what diseases you might get in the future or how you should eat or exercise.

A new wave of consumer DNA tests that will analyze our genetic makeup promises to offer clues, from risk for different kinds of cancer and heart conditions to how we process certain foods or whether we’re likely to weigh more than average.

Yet amid this windfall of personalized insights, the question remains: Would we actually use this information to make positive changes in our lives?


Public health researchers are eager to know the answer, as the industry explodes. The number of people who purchased kits online doubled from 6 million to 12 million in 2017. One study found that nearly one-third of more than 1,000 people reported their results had motivated them to eat more fruits and vegetables and engage in more strength training.

“A lot depends on why they got the tests. These were early adopters of genetic testing and information seekers who are naturally more motivated,” says the study’s co-author, Catharine Wang, a public health researcher at Boston University. “But we still don’t know if they will keep up with these changes over the long run.”

Part of the challenge is getting people to take health risks seriously because those potential harms feel far off in the future, adds Theresa Marteau, director of the Behavior and Health Research Unit at the University of Cambridge who found that genetic testing generally didn’t lead people to change their behavior, including stopping smoking, drinking less alcohol or achieving a healthy body weight. “The immediate pleasure of eating chocolate is more powerful than the uncertain future consequences of being overweight, for example,” she says.

Yet people paid attention to serious health reports when their behavior had more immediate effect.

If you learned you had a genetic risk for hereditary forms of breast, ovarian or colon cancer or dangerously high cholesterol as part of a condition known as familial hypercholesterolemia (FH), you’d be more likely to see a doctor or seek out follow-up testing, says Scott Roberts, a health behavior researcher at the University of Michigan. “If people suspect they have a family history of the disease — and the test suggests they have a higher risk — then that can be extra motivational,” he says.

Also, people were more likely to make long-term changes if they learned of a specific action to take, rather than receiving generic advice to “be healthy.” In one study, people who discovered they have the genetic variant that increases one’s risk for late-onset Alzheimer’s disease were more likely to start taking certain vitamins or supplements that were linked to brain health, says Roberts. Other research has shown that people had a better of chance of sustaining behaviors if they were paired with a support group or workplace wellness program, such as smoking cessation, exercise or nutritional counseling, he says.


The big picture might matter as much as the nitty-gritty. Dr. Dan Reardon is co-founder of FitnessGenes, a genetic testing company that provides nutritional and exercise insights, such as how you metabolize saturated fat or caffeine or how many weight reps are best for your body composition.

Reardon says clients also followed general advice, such as when to exercise based on their natural sleep and wake cycles. “If you’re a night owl, morning workouts won’t lead to the best results,” says Reardon. “Even knowing what time of day to work out can set you up for success.”

Although experts agree that such self-knowledge is generally empowering, even a seemingly discouraging result can be inspiring. In a study that looked at how people responded to news they carried a gene associated with obesity, psychologist Susanne Meisel of King’s College London said they reported a “relief of self-blame” in their difficulties with weight control and used it as extra motivation. “They reframed it as ‘This means I have to work hard because I’m battling my biology. I can’t change my genes. But I can change what I do every day,’” she says.

What’s out there

Here are a few of the many popular DNA tests on the market. If you’re interested in trying one, it’s might be worth discussing with your doctor beforehand: He or she might have suggestions on what to look for, or a test preference.

23andMe, $199


The Health + Ancestry Service includes more than 90 reports on your ancestry, traits and genetic health risks, such as selected variants for the breast and ovarian cancer genes BRCA1 and BRCA2, late-onset Alzheimer’s and Parkinson’s diseases and celiac disease.


FitnessGenes, $289

The company’s most comprehensive “Get Fit” product offers a DNA analysis and 12-week nutrition and exercise plan, including insights on your capacity for aerobic exercise, whether you can tolerate high glycemic load foods and how long to rest between resistance training sets.


Invitae, $350


The “Genetic Health Screen” analyzes 147 genes to determine your risk for 10 kinds of cancer, heart conditions, high blood pressure and cholesterol, a disorder that can cause you to absorb too much iron from your diet, a disorder that can lead to lung or liver disease and several other conditions.