Well, I've been having problems for years. Finally about 3 years ago, I managed to lose 50 pounds one year by eating almost nothing and going on 7-mile hikes five times a week. I think I wore out my knee cartilage, though. And I started getting overtraining symptoms, though I didn't understand at the time what they were. (Until I came to this forum, I had no explanation for the weird panic attacks I was going through!)
Then I slacked off a couple years, and 20 pounds came back...
This year I started with the biking (easier on the knees) and eating healthy, normal meals. In fact, what with energy snacks and stuff, I believe I am eating more than I did before, and I've lost 15 pounds this summer! The trick, like IowaParamedics, is commuting 64+ miles per week, plus longer trips on weekends. (I'm also at a point where it is creeping down by ounces, though.)
And now, when I trash my diet, I have the option to run outside and work it off on the bike.
Still, got a long way to go....