I'm fine with the idea of having measures of healthy living, much like we do for driving. We would need to make sure though that they're objective. For instance, while obesity is a problem, a lot of studies are showing us that it's actually more healthy for some people to stay their heavyset size than to struggle to lose weight and gain it right back. A person's fitness level, cholesterol level, etc., are much more important in determining whether the person is taking care of him/herself. We also need to be careful to take into account whether a person has another medical condition that prevents what we'd consider optimal diet and exercise. We can't have the same fitness standards for a typical person as we do for someone with severe orthopedic or neurological conditions, or for someone with major mental illness.
The feds have (had? I know it's changed and believe the name might now be different) a program called Medicaid Rehabilitation Option, which employs Performance Based Contracting for programs that provide support to people with mental illness who live in group homes or in apartments where staff visit them to provide support. In this program, in order for the program to be paid, the program had to demonstrate that 75% of people were meeting 75% of their goals. The goals had to be rehabilitation goals rather than quality of life or maintenance, but they were quite individualized. In other words, they weren't measuring "health" for each person based on whether that person had a job, was raising a family, and was driving a car. For some people, the person was making progress by deciding that she wanted to go out and buy a newspaper twice a week so she could get out of the house and be more in touch with what was going on in the world. For another person, it was making his own coffee. For some people, yes, it was getting a full-time job or getting into college. But the goals were individualized by the staff (with client input except when a client was really unable to express preferences) to push each person to be a little more independent and engaged in life. Not to try to get every person up to the same standards.
Something like this would make sense with physical health care. A provider and patient would come up with fitness and lifestyle goals that were appropriate to the person's physiology, other physical health concerns, and mental health. People who were meeting their goals, thus showing an investment in health, could get a discount on their health insurance. It would be similar to how my plan gives me $150 per year toward a gym membership. We'd need to be careful that we're giving bonuses to particularly motivated people, rather than making insurance impossibly expensive for people whose health suffers because they're under tons of stress because of factors in their life they can't control. (There was recently a study showing that Black families have a much higher rate than whites of low-birth-weight and/or premature infant births, even when controlled for by income, education level, family stressors, etc. Leading to the conclusion that daily effects of racism itself cause stress, which we know is linked to intrauterine growth restriction and pre-term labor.)