It may save the employer , so ultimately the taxpayer money That's sensible in my book.
From the US but probably still relevant
Example - Employee Health Concern: Obesity
Relev- Normal-weight men miss an average of 3.0 days each year due to illness or injury
- In comparison, overweight and obese men (BMI 25-35), miss approximately 2 more work days per year than normal-weight men, a 56% increase in missed days
- Normal-weight women miss an average of 3.4 days each year due to illness or injury
- In comparison, overweight women miss 3.9 days, a 15% increase in missed days; obese women (BMI greater than 30) miss 5.2 days, a 53% increase in missed days; and women with a BMI of 40 or higher miss 8.2 days, a 141% increase in missed days, almost one week more of missed work each year than normal-weight http://www.cdc.gov/workplacehealthpromotion/businesscase/benefits/productivity.html