Exercise is important for fitness, but it's really irrelevant for weight loss. For a male, running burns about 100 net calories per mile: http://www.runnersworld.com/weight-loss/how-many-calories-ar... (depending on weight). To achieve a weight loss of one pound per week, you have to run five miles a day every day. If you're out of shape, that'll take an hour a day, every day, time you almost certainly don't have.
Exercising your way to weight loss is an incredibly inefficient use of time. And telling people that they shouldn't even try to lose weight until they can fit in daily exercise into a schedule that's already full is needlessly setting them up for failure.
As a runner for the past 23 years, you really, really do have a whole hour a day to dedicate to moving.
I assure you that your body will fall apart sooner than later if you dedicate no time to keeping it strong and limber.
I'd also say consumption is closer to 120 calories per mile. 3600 calories per lb. of fat so ~30 miles = 1 lb. I usually advise 5 times a week x 3 miles as a beginner program (after a moderate buildup of walk/run and less days per week). So every two weeks our subject would lose 1 lb. That's 26 lbs. in a year.
Assuming these are 12 minute miles (which is just a bit faster than a walk), 12 x 15 miles = 3 hours a week. That is really a bare minimum of activity. If people start doing this at age 25 or so instead of trying to start at 45 when they are 60 lbs heavier than they should be it's not too difficult.
Exercising your way to weight loss is an incredibly inefficient use of time. And telling people that they shouldn't even try to lose weight until they can fit in daily exercise into a schedule that's already full is needlessly setting them up for failure.