Depends on your current weight and how active you are that day. It won’t be much…less than a pound. If you lose more, it is water loss and will return when you eat and drink normally.
Better to establish the weight you prefer to be, and consume calories that will sustain that weight.
An occasional one-day fast is not harmful, but habitual and frequent fasting is not a healthy way to lose weight.
The weight you will lose will be mostly water weight. It can be as high as 2Kg or even 3Kg because approximately 500g of glycogen is stored in our body which is bonded to 3 times as much water. Note the weight loss is not fat loss in this case. One day of irregular fasting may not burn fat. Most of the energy needs on one day fasting can be met by glycogen storage. On the third day, entire weight will be gained back as the weight lost was water weight and stored energy (glycogen), which will be replenished on the day after fasting.
I tried this and ended up losing 15 pounds in a week, I ate very little, about 500 or less calories every other day, no exercise my weight was 210, I wasn’t happy that my clothes, especially my underwear, wasn’t fitting me because, I do not like to shop for new clothes, then things got bad, I drop down to 180, I started eating again and went back to 200 pounds all of this in a month.
Whilst skipping meals to get rid of weight is not really recommended, knowing how many calories you are able to burn in eventually without food is really a basis for the number of calories you ought to take in every day. Your basal metabolism, or BMR, tells you the quantity of calories your body needs should you were in which to stay bed for twenty four hours. This formula is dependent on your age, sex, height and pounds.
You shouldn’t actually do that. All you’ll lose is muscle and water weight, which is almost immediately gained back after returning to normal eating habits. Better focus on a moderate fat loss approach, that goes far beyond one single day and hasn’t you suffering from starving.