Maintaining a healthy weight is about more than just achieving a perfect body. While you might like to have a nice beach body, a healthy body weight may reduce your risk for chronic disease, such as cardiovascular disease and some types of cancer. While there is no such thing as a "perfect" body weight, there are several methods that can help you determine a healthy weight range.
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Body Mass Index
Health professionals commonly use Body Mass Index--or BMI--as a tool to calculate healthy body weight for adults. A healthy BMI is considered to be between 18.5 and 24.9. To determine the weight in pounds that will put you at a BMI right in the middle of that range, take your height inches and square it, then multiply by .03087. (Ref 1 How is BMI Calculated--with formula extrapolated). For example, if you are 5 feet 5 inches tall, your ideal weight would be 65 inches x 65 inches x .03087, which is 130 pounds. At this weight and height, your BMI would be 21.6.
If you are an athlete or have a lot of muscle mass, your perfect weight will be higher in the healthy BMI range. The reason for this is that muscle has a greater density than fat, meaning an individual with a lot of muscle mass may actually be heavier than an individual of the same size that has more fat mass. To calculate the weight that would give you a BMI of 24.9, multiply your height in inches squared by .03542.
If you have a tiny frame and not a lot of muscle mass, your ideal weight may fall at the lower end of the healthy BMI range. Multiply your height in inches squared by .02703 to calculate the weight in pounds that would put you at a BMI of 19.
Healthy Weight for Your Age
Although the BMI measure is intended to be used for all adults ages 20 and older, it may not be an accurate measure in older adults. Muscle and bone both weigh more than fat, by volume, and BMI does not differentiate between different types of tissue. Both bone density and muscle mass tend to decrease as individuals age, making BMI a less reliable assessment of body weight. The BMI goals are based on weights at which risk for chronic disease and mortality is the lowest. For adults over the age of 70, mortality rates were found to be the lowest in those with a BMI between 25 and 29.9, according to a 2010 study published in the Journal of the American Geriatrics Society. (Ref 6) This BMI range is generally considered to be overweight, but if you are over 65, your ideal weight will likely fall into this range.
Using Body Fat Percentage to Calculate Ideal Weight
Calculating your perfect body weight involves more than the number on the scale. While BMI can give you a good target range to shoot for when you step on the scale, your body fat percentage may give you a more specific assessment body composition. (Ref 3, last paragraph) A pound of bone or muscle takes up less space than a pound of fat. This means that a fit and trim person with a lot of muscle may weigh the same as a larger person, but the fit one is likely healthier. Some fat is essential for basic metabolic functions and to protect major organs, but most individuals have additional fat stored that is not necessary. A doctor or a fitness professional can measure your body fat percentage. According to the American Council on Exercise, a healthy body fat percentage is anywhere between 14 and 31 percent. Athletes generally fall between 14 and 21 percent, but if your goal is to be trim and fit, you should aim for a body fat percentage between 21 and 24 percent. (Ref 9)
Wait-to-Hip Ratio Can Help You Evaluate Your Shape
Another way to estimate your ideal body weight is by measuring your waist-to-hip ratio. Your waist size and body shape plays a significant role in determining your risk for chronic disease, according to the University of Pittsburgh. (Ref 10) If you carry excess fat in your hips and thighs, you are at a lower risk for disease than an individual of the same weight that carries excess fat around the abdomen. (Ref 10) To calculate your waist-to-hip ratio, measure your waist at its smallest part and your hips at the largest part. Divide the waist measurement by the hip measurement. The lowest risk is at a ratio less than 0.9 for men and less than 0.8 for women. (Ref 7, Method 2) Even if you fall within the healthy range for BMI, your ideal weight may be lower in order to decrease your waist-to-hip ratio.