More importantly, even if employees make some personal decisions that affect their performance in somewhat negative ways, they're still people and are still worthy of jobs and the ability to live well. If a company starts firing or making promotion or bonus decisions based on an employee's "healthy lifestyle" or optimization of their personal habits as they relate to work, they had better be prepared to be sued when new medical opinions about what that entails crops up.

And they'd better be prepared to lose overtime, especially from salaried workers. Many studies have shown that working longer hours degrades performance. If you're going to insist that I drink coffee or don't have a candy bar and my job depends on this then I will sue you if I'm required to work any hours over what the best science suggests.

If businesses have any sense (and there is little evidence that many do) they'll stay out of this minefield. People are not machines and cannot be graded as such.