I'm trying to lose weight...anything tricks?

I've been overweight my entire life, it's in my family, but I've also been trying to lost weight for the last 3 years. I know about cutting calories, writing down everything you eat etc. I went to a nutritionist and she didn't really help b/c I already eat really healthy (organics, lots of veggies, oatmeal, etc.) Does anybody have tips besides don't eat or anything like that? I'm 19, a competitive swimmer (5x1.5 hour practices a week with some weights and dry-land Incorporated), and weigh 255 lbs. Thanks!