A: Offending someone—though a worthy concern—is actually the least of the potential issues raised by doing this.
1. The school isn't the employee's doctor, so it has no way of knowing who should or should not lose weight for health reasons.
2. Encouraging all employees to achieve the best level of health that they can is one thing; advocating weight loss specifically is quite another.
3. While it is kind-hearted in intent, taking such a position with an employee can quickly run afoul of the Americans With Disabilities Act (ADA) and related state and local statutes (i.e., for employers, the primary issue is whether or not the employee is capable of fulfilling their job duties, with or without "reasonable accommodations").
With all of this in mind, we would suggest two ideas.
1. If the employee's weight appears to be negatively impacting his/her job performance, consult with an employment attorney on the specifics of the situation. It is possible that this can be addressed directly and with dignity within the bounds of the ADA.
2. If the employee's weight isn't negatively impacting job performance the most that the school can safely do is, institute a VOLUNTARY wellness program open to all employees. Even well-structured wellness programs have begun to be questioned on ADA grounds, so be sure to get professional advice before starting one. Health carriers can often provide direct guidance and assistance in starting legal wellness programs.