a pound of fat is 3500 calories. the average calories an adult human needs is roughly 2000, depending on height, sex, and level of activity. if you want to lose 5 pounds a week you would have to be literally starving, not eating at all. please do not aim for that. healthy weight loss is 1-2 pounds a week. any faster than that and you start running into lots of problems. talk to your doctor if you want help on this journey!
As someone who’s lost weight fast and lost weight slowly. Pick slow, and put your water intake through the roof. Helps MASSIVELY with loose skin. Faster you loose weight, the more you deal with stretch marks too. Yes it’s frustrating to not make a dramatic change quickly, but it’s a lasting change. Wayyy easier to make a small lifestyle change than pivot to an on again off again diet and hope not to put back on the weight with the behaviors that got you there in the first place.