Your ideal weight depends on your height. No single weight is perfect for you; you can be fit and healthy at a range of weights. Body fat is more important than the number on a scale. To determine if you are at a healthy weight for your height, you need to determine your body mass index, or BMI.
Body Mass Index
BMI is a figure calculated from your weight and height that reliably indicates body fat. It is used as a screening tool to estimate your risk of possible health problems, such as hypertension, type 2 diabetes, stroke and gallbladder disease. Calculating BMI is inexpensive and easy to do. Other methods to measure body fat, such as skinfold thickness measurements, underwater weighing, bioelectrical impedance, dual-energy x-ray absorptiometry and isotope dilution, are more costly and difficult to access.
Calculation
To calculate your BMI using the metric system, divide your weight in kilograms by your height in meters squared. Height is commonly measured in centimeters, so divide your height in centimeters by 100 to obtain your height in meters. If your BMI is below 18.5, you are considered underweight. A BMI of 18.5 to 24.9 is considered normal, while a BMI of 25 to 29.9 is considered overweight. If your BMI is higher than 30, you are considered obese.
Considerations
BMI is not the only measure of body fat and is only one factor related to disease risk. Abdominal fat also predicts risk for obesity-related diseases. Other important factors include physical activity level and high blood pressure. Note that the interpretation of BMI for children and teens is age and sex-specific. Fat tends to vary greatly with age because children go through periods of rapid growth. Girls also tend to have more fat than boys.
Limitations
Note that some individuals, especially athletes, may have a high BMI but not a high percentage of body fat because of more muscle mass. BMI may underestimate body fat in older persons and others who have lost muscle. To get a better idea of whether you are at risk for obesity-related health conditions, measure your waist. Stand and place a tape measure around your middle, slightly above your hipbones. Measure your waist right after you breathe out. Risk is highest for women with a waist circumference of more than 35 inches and men with a waist size that is greater than 40 inches.
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