An empty calorie refers to a food item that adds no nutritional value to your body. It includes foods such as crisps, sweets, chocolates, and cakes. In other words, there is very little that your body can extract from them in terms of good nutritional value out of that particular item.
Your body will also not be able to store anything from it in a meaningful manner. So, although you are adding tonnes of calories in the form of refined sugars, saturated fats, refined carbohydrates, and spices, you have not matched that caloric intake with adequate nutritional value.
Therefore, the body cannot use the calories in a manner that keeps the body healthy. The gland within your brain that senses and processes your caloric intake will not know the difference between whether you have taken in a good calorie or a bad calorie. As a result, it will not encourage you to go and consume good, nutritious calories once you have completed eating all of the empty calories.
All it knows is that it has consumed its daily 2000 to 3000 calories for the day. You, therefore, have to be disciplined about guiding your body and managing your food intake.