A calorie is a calorie whether it comes from fat or carbohydrate.
Anything eaten in excess can lead to weight gain. You can lose weight by eating less calories and by increasing your physical activity.
Reducing the amount of fat and saturated fat that you eat is one easy way to limit your overall calorie intake.
Eating fat-free or reduced-fat foods isn't always the answer to weight loss. This is especially true when you eat more of the reduced fat food than you would of the regular item. If you eat twice as many fat-free cookies you have actually increased your overall calorie intake.[/list]
Remember:
Just because a product is fat-free, it doesn't mean that it is "calorie-free." Every calorie counts!
Source: nhlbi.nih.gov