There are 7700 calories in 1 kilogram of body fat.
Since there are 3500 calories in 1 pound of fat and there are 2.2 pounds in 1 kilogram, you can easily work out that there are 7700 calories in 1 kilogram.
So if you wanted to lose weight at a rate of 1 kilogram per week, you would need to reduce your overall calorie intake by 7700 calories, or 1100 calories per day.