I should be using fat free salad dressings, right?

Actually, no, and for two reasons:
1) When chosen wisely, fat is a very important part of your diet. Healthy vegetable fats, like olive oil and canola oil found in salad dressings, have been associated with a reduced risk of heart disease, stroke and type 2 diabetes.

Fats also help to stabilize the blood sugar. A stable blood sugar will reduce hunger and make it much easier to lose/maintain your weight.

2) Low fat dressings are notoriously high in sugar.  In an effort to improve the taste of a dressing without fat, manufacturers add in sugar. If weight loss is your goal, sugar in your diet will spike your blood glucose and insulin levels, which promotes hunger and fat storage.

Here are some recommendations on salad dressing:

1) Skip the low fat dressings; you want a healthy fat as part of your meal.

2) Go for oil based dressings like Italian, olive oil and vinegar, or olive oil and lemon juice.

3) Avoid creamy dressing like Ranch, French, Thousand Island, Russian, etc.  These are high in saturated fat and have the potential to raise LDL cholesterol.

4) Avoid dressings like Honey Mustard and sweet vinaigrettes which are loaded with sugar.

5) Keep portions reasonable.  Oils are high in calories and it is easy to go overboard. I have my female clients shoot for 1 tablespoon of oil at a meal, which would be 2 tablespoons of oil and vinegar or Italian dressing. Men can do 1½ tablespoons of oil per meal.