08 Mar 2013 A calorie deficit is the magic that makes weight loss possible. It is the difference between the amount of energy you burn and eat; the shortfall of energy caused by eating less and moving more. If your body burns 2,000 calories per day and you only eat 1,500, that extra 500 calories comes from non-food sources (typically body fat) causing weight loss. Creating a healthy calorie deficit requires exercising more, monitoring your food intake and making smart food choices. Here are a few ways to ruin a calorie deficit and create a failing weight loss strategy.