Healthcare premiums being what they are, companies are trying to bring down costs by encouraging workers to get healthier.  Maybe they pick up part of employees’ gym membership tab. But the pharmacy chain CVS is planning a wellness program with a twist. CVS will require employees to disclose their weight and other health benchmarks — or pay $600 more for health insurance.

The data-driven program has inflamed privacy advocates. It’s also an open question as to whether these programs can achieve their goals of making people healthier and saving money.

Still, “wellness is sort of the flavor of the month,” says Soeren Mattke, managing director of RAND Health Advisory Services.

CVS is just the latest to serve it up, and it played down the change, saying that many American companies incorporate health assessments into their wellness programs. And, the company says it won’t see any personal health data.

Nonethless, this type of program raises red flags for people like Dr. Deborah Peel, founder of Patient Privacy Rights. She worries about the potential for abuse of the data. And she scoffs at CVS’s description of the program as voluntary.

“How many people can afford to have $600 deducted from their paycheck every year?” Peel asks. “Not that many that I know of.”

UCLA law professor Jill Horwitz recently studied the results of various company wellness programs. It’s not at all clear these programs are actually making workers healthier.

“Even if they are able to change their behavior, the evidence is pretty mixed that those behavioral changes translate into changes in health status and then changes in health spending,” Horwitz says.

Even if wellness programs do work, notes RAND’s Mattke, the results won’t always be immediately apparent.

“If you change somebody’s health related behavior today, it may take quite a while until you see tangible savings in health care costs,” he says.

The worst consequences of unhealthy living may not show up until old age, when people are on Medicare, and taxpayers get stuck with the bill.