...you can eat fairly well, work your butt off all summer and drop some significant weight. But if you don't adjust your diet, that weight will come back as soon as you ease up on those massive workouts. I've dropped 50 lbs over the spring/summer/fall, only to replace over half of those pounds over the winter. Rinse and repeat. I don't think you'll maintain your long term goal until you have settled on a reasonable sustainable diet that will maintain your weight.

From that point you have two options to lose weight. You can (a) temporarily adjust that diet to reduce calories, putting yourself in a calorie deficit to lose weight, or (b) you can increase your work outs to where you're burning more calories than your "base diet" can support, thus you lose weight.

There is a 3rd option, where you do both (a) and (b) simultaneously.

Once you reach your optimal weight, you'll need to adjust the diet you had when you were heavy down to whatever will maintain your new "current" weight. If you regularly hit the scales, you'll know if you need to adjust your diet.

When it comes to "low fat" vs "low carb" diets, the studies I've read is that both will help you lose weight. The difference between the two is that "low fat" will drop weight, but it doesn't target your fat stores. Frankly if your body sees itself in a low fat calorie deficit, there's a good chance it will think you're in a (caveman) "starvation" status, and do what it can to maintain the fat stores by eating your muscle mass. "Low Carb" diets, on the other hand, do a much better job targeting your fat stores. Most, if not every, diet study has determined people will lose more body fat by eating a "low carb" diet than a "low fat" diet.

OK, off my soapbox! :)