The cause of excess weight can be easily explained: People gain weight when they consume more energy through food than their body burns. The excess is stored in the form of body fat in the fat cells in "times of need." If you are overweight, you have probably eaten too much or moved too little, or both. When one looks more in detail at the explanation for the development of excess weight, a variety of causes can be held responsible. The elimination or consideration of those causes are important steps toward achieving one's desired weight.