The term "fat burning" refers to the process by which your body uses fat as its primary energy source. This typically occurs when you are consuming fewer calories than you need for maintenance, or during periods of fasting or prolonged exercise. During these times, your body starts breaking down stored fats in order to provide energy for essential bodily functions and physical activity. The process of burning fat can lead to weight loss as well as improved health outcomes such as reduced risk of heart disease and diabetes.