Why are employers implementing policies that require employees to adopt healthier lifestyles?

What can an organization do to ensure that merit pay and other incentives are administered fairly? What kind of data would you gather to ensure that the pay-for-performance system is not biased in favor of any particular group? Would linking pay to objective criteria that are important to the organization, such as quality control measures, profitability, and low turnover, help or hurt in administering pay?
Then choose from 1 of the following:
Why are employers implementing policies that require employees to adopt healthier lifestyles?