John Hancock and Vitality, which is owned by Discovery, said the information would not be sold and would be shared only with entities that help with the program’s administration, though the aggregate data could be used to inform the development of new insurance products.

Nonetheless, some specialists expressed privacy concerns.

“All of a sudden, everything you do and everything you eat, depending on which bits of the information they collect, is sitting in someone’s database,” said Anna Slomovic, lead research scientist at the Cyber Security Policy and Research Institute at George Washington University and a former chief privacy officer at Equifax and Revolution Health.

Of course, buying any life insurance policy requires customers to share detailed medical histories upfront. But consumers participating in the Vitality program must be comfortable providing enough information continuously to meet certain thresholds that will convert into worthwhile savings. That might include the frequency of workouts, reporting a physical exam or answering sensitive personal questions: During the last 30 days, how often did you feel so nervous that nothing could calm you down? Hopeless? Depressed?

“You do not have to send us any data you are not comfortable with,” Mr. Doughty said. “The trade-off is you won’t get points for that.”

Participants need to amass 3,500 points to achieve silver status, 7,000 to reach gold and 10,000 for platinum. Nonsmokers automatically earn 1,000 points, and people with in-range cholesterol, glucose and blood pressure will receive 1,000 points for each. A “verified” standard workout three times a week, or an advanced workout twice a week, provides another 3,120 points over the course of a year. Flu shots, 400 points. The clock is reset each year, though 10 percent of points may carry over.

All customers participating in the program will start by paying a premium priced at the gold level. That is a discount of about 9 percent for a 45-year-old man who bought a $500,000 term insurance policy that covered a 20-year period: He would pay $750 annually, compared with the $825 it would cost outside of the Vitality program.

So what if he does everything right, but breaks his leg? Or worse, gets a serious disease like cancer? While those conditions would not directly affect his rate, if he could not maintain gold status for any reason, he could see premium increases of 1.1 to 1.6 percent each year. But if he reached platinum status, his premiums would fall by about 0.30 percent each year.