When you eat “light” products you will not gain fat.

A calorie is a calorie, regardless whether it is composed of fat or whether it is labeled “light.” Just because a product such as cookies is so labeled, it does not mean that we have unrestricted permission to feast out of control and stuff ourselves. Light products are so called because they have a lower percentage of one of the nutritional components compared to the normal version of the product. They may have less fat but they will probably have more sugar to compensate the taste.