BAKERSFIELD, Calif. -- Companies such as 23andMe and Navigenetics offer consumers genetic testing for a range of illnesses, including information about heart disease.

Proponents say the results will let people know their risk factors early, when it is still possible to reduce the odds of disease through weight loss and exercise.

But a new study published in the Journal of the American Medical Association has suggested the tests aren't actually very helpful when it comes to predicting a person's future risk for heart disease.

Researchers analyzed the DNA of 19,000 women for dozens of tiny mutations that were linked to heart disease. But once doctors factored in traditional risk factors such as family history, age, and cholesterol levels, the genetic score did not add any additional predictive ability.

The findings indicated that genetic tests create added cost without providing much added information about a woman's future heart risk. Besides, suggested doctors, patients shouldn't need an expensive test to tell them to eat better and get more exercise.