Some studies have found that distance-based goals are more effective than time-based goals when trying to lose weight. But researchers also acknowledge that there is little evidence to support a strong recommendation either way. The best goal for you may depend on your lifestyle. If your schedule only allows for a certain amount of time on a given day, then set a goal for time rather than distance. If you feel energised by the idea of reaching distance milestones, then set a mileage goal.