Do you think your metabolism knows what time it is? While your body does run according to a circadian rhythm, your metabolism does not shut down at night. You still need to provide your body with fuel to repair and rebuild while you sleep, and to prevent it from going into a catabolic state brought on by a long period of fasting. This is especially important if you work out later in the day.
After a workout, your body is crying for a good source of carbohydrates, so don’t skimp because you think eating at this time will make you gain fat.
It is important to make sure you are eating healthy foods later in the day — such as lean meat, healthy fats, plenty of vegetables, and even some complex carbohydrates if you are really active later in the day — to reduce your risk of adding unwanted body fat, but there is no need to avoid eating at night altogether.