Always trim all visible fat from meat, and discard poultry skin. Watch calories and portion sizes. It is possible to mess up a low-fat diet. Most low-fat diets are low in calories, but not all are. It simply isn't true that you can eat whatever you want, in any quantities whatsoever, as long as you stick to low-fat foods.
Calories do count.
And if you increase your calorie intake on a low-fat diet and gain weight, that will cancel out many of the benefits you would get from cutting down on fat.