We are putting on weight when we eat more calories than our body really requires or can use for its every day activities. We need a certain amount of energy to work in a proper way and depending on the activity we performing, this energy expenditure fluctuates. For example, the amount of calories that were burnt during running will be bigger than just walking for the same distance or time. The excess calories that we get from the food are stored in the body for using in the future. The principal secret of effective weight loss is burning larger amount of calories than consumed.