I use a calorie counting app every day. It's stunning how much we eat when you count every damn bite. My sister turned me on to it back in 2007 or 2008. She lost 100# with it and has kept it all off since. She works out hard and is careful with how she eats, but she is now the fittest 51 year old woman I've ever seen (her arms make most guys jealous).

It's just as important to eat the right stuff, but simply counting calories is an excellent start. Assuming your app lets you add back calories burned from exercise, it's also an excellent motivator to go get a workout. If you're trying to lose 2# a week, you probably only get somewhere on the order of 1,400 - 1,600 calories a day. The extra 150 calories per mile makes a run seem like a great deal.