One of my former employers had an excellent wellness program that did motivate quite a number of employees ...at different times for different activities.

In working with the wellness coordinator, your company might want to partner with non-profit organizations ie. the YWCA/YMCA, local cycling group that already have someone who has information to provide a lunch hr. session, etc.

this employer brought in a trained kinesiologist where person did take body fat measurements, weight and gave info. as starting point for interested employees.

For cycling, walking or running activities, consider a fun cumulative mileage/distance thing which perhaps one could visually show on a map over time and as a visual motivator.