Exercise is certainly helpful once you start getting close to your ideal caloric intake. If at rest you'd burn ~2000 cal/day, and you're consuming ~2300 cal/day

Exercise is certainly helpful once you start getting close to your ideal caloric intake. If at rest you'd burn ~2000 cal/day, and you're consuming ~2300 cal/day, then exercising for one hour, three days a week can certainly make a difference. Most people that are actually overweight though, have a much higher surplus in their caloric intake. Strenuous exercise like running over 10km isn't possible for many of these folks... and even if it were, it certainly wouldn't be possible every day. Cutting out the 600cal breakfast sandwich in the morning or the 200cal soda every day at lunch will have a bigger impact for most folks and is a lot more feasible.