Please tell me how long it takes for to lose 100 pounds without exercising?

3500 calories/1lb: You have to cut down 3500 calories in your diet to loose one pound if you cut down 500 calories per day, you will loose 1 pound in on week, and approx 4 lbs in a month your weight loss is based on calories you reduce in your diet if no exercise so calculate for yourself, if you are negative 3500 cals per week, it will take 100 weeks. If you reduce more calories you loose faster than that.