In order to lose weight you must consume fewer calories. Lesser calorie intake means all the calories are being used by the body and not stored as fat.
The number of calories from your daily consumption that you aren't able to burn during the day is called the Daily Calorie Deficit. This means that if you consume 2500 calories and burn only 2000 calories during the day, you have a daily calorie deficit of 500. This excess of 500 calories is what’s stored as fat in the body.
The fat in the body can only be melted if you burn more calories than you actually consumed during the day. When you consume less calories than you burn, the body will get its additional energy requirements from the stored fat in the body. This means that you will end up losing weight.