I dropped 40 pounds in a year by running as much as I could (30-40 miles a week) drinking way less, no snacks and no desserts. From what I've read diet accounts for about 85% of weight loss. From my personal experience I'd say it's pretty accurate. One tip I found worked for me was to try to choose food by how it makes you feel and not how it tastes. That and being patient can make a huge difference.