NEW YORK — If you learned your DNA made you more susceptible to getting a disease, wouldn't you work to stay healthy?You'd quit smoking, eat better, ramp up your exercise, or do whatever else it took to improve your odds of avoiding maladies like obesity, diabetes, heart disease or cancer, right?The scientific evidence says: Don't bet on it.DNA testing for disease risk has recently expanded in the U.S. The company 23andMe recently started selling the nation's first approved direct-to-consumer DNA tests that evaluate the buyer's genetic risk for certain disease or conditions. That go-ahead came in April, about three years after it was told to stop selling such kits until it got the OK from regulators.The field also gained a new entrant in July, when a company called Helix launched an online marketplace for DNA tests, including some for genetic health risk. Helix decodes a consumer's DNA and passes the results along to another company for analysis.