Everyone is different, and there may not be one magic number.
"No one really knows the precise answer, so this is something you want to negotiate with your physician," says Richard Weil, weight loss program director at the New York Obesity Nutrition Research Center.
Many doctors will simply use body mass index as a guide. BMI uses your height and weight to gauge whether you're underweight, at a healthy weight, overweight, or obese. Everyone is different, though.
"If you're middle-aged, have been overweight for a long time, and your doctor says you ought to get to the weight you were in high school, that might not be realistic," Weil says. Work with your doctor to pinpoint a number that's achievable and sustainable.
2. How long should it take me to reach my goal?
Most experts advise losing no more than 1-2 pounds per week. "Really rapid weight loss is mainly water or muscle and not a lot of fat," says Melina Jampolis, MD, a physician nutrition specialist in Valley Village, CA, and co-author of The Calendar Diet.
However, she says it's generally OK to drop 3-5 pounds a week for just the first few weeks, especially if you're more than 30 pounds overweight.
3. How will losing weight impact my health?
You know that losing extra weight is good for you, but you may not know all the benefits.
Press your doctor for some specifics. "If you learn that losing 5% to 10% of your weight would enable you to get off your blood pressure medication, that's extremely motivating," Jampolis says.