> Very roughly, there’s 3500kcal in 1lb of body. Given that fact plus your current weight and calorie intake, you can build a spreadsheet in 30 mins to compute the calories per day to make your body any weight you want in a reasonable time frame
emphasis on the very roughly ... a significant part of body mass is tissue you do not want to lose: bone, brain, organs
1lb of fat is ~3500 calories and that is simply 9 calories per gram of fat X 453 grams in a pound. its actually closer to 4000 but people just use 3500 because that means you would need a 500 calorie deficit per day to lose a pound a week.
emphasis on the very roughly ... a significant part of body mass is tissue you do not want to lose: bone, brain, organs