How Much Should I Weigh

Although only nature knows the best weight for your body, the following guidelines offer a method to estimate the midpoint of a healthy weight range (plus or minus 10 percent, depending on whether you have large or small bones). This rule-of-thumb guide does not apply to everybody— especially muscular bodybuilders.

  • Women: 100 pounds for the first 5 feet of height, 5 pounds per inch thereafter (45 kilograms for the first 152 centimeters, 0.9 kilogram per centimeter thereafter).
  • Men: 106 pounds for the first 5 feet of height, 6 pounds per inch thereafter (48 kilograms for the first 152 centimeters, 1.07 kilograms per centimeter thereafter).

For example, a woman who is 5 feet, 6 inches (168 centimeters) could appropriately weigh 100 + 30 = 130 pounds (45 + 14 = 59 kilograms), with a range of 117 to 143 pounds (53 to 65 kilograms). A man who is 5 feet, 10 inches (178 centimeters) could appropriately weigh 106 + 60 = 166 pounds (48 + 27 = 75 kilograms), with a range of 149 to 183 (68 to 83 kilograms).

Although athletes commonly want to be leaner than the average person, heed this message: If you are striving to weigh significantly less than the weight estimated by this guideline, think again. Pay attention to the genetic design for your body, and don't struggle to get too light. The best weight goal is to be fit and healthy rather than sleek and skinny.

If you are significantly overweight, your initial target should be to lose just 5 to 10 percent of your current weight. If you weigh 200 pounds (91 kilograms), losing just 10 to 20 pounds (5 to 10 kilograms) is enough to improve your health status and significantly reduce your risk of heart disease, diabetes, and high blood pressure. Although you may want to lose more fat for cosmetic reasons, you should know that losing the initial few pounds is a meaningful accomplishment.

Body Mass Index

The body mass index (BMI), a ratio of body weight to height, is often used as a screening tool to identify people who are overfat (BMI greater than 25) or obese (BMI greater than 30). In the general population, people with a high BMI are considered to have excess body fat and to be at risk of developing heart disease, diabetes, and other medical concerns. Yet, BMI is a poor method to screen for overfatness in athletes because it accounts for body mass, not body fat. Hulky football players, weight-lifters, and other power athletes who have lots of muscle mass easily get ranked as "obese"; this is generally far from the truth. In a study of 28 collegiate hockey players, the average BMI was 26 (overweight), but the average body fat was a lean 13 percent. Among 149 male wrestlers and basketball, hockey, and football players, 67 percent had a BMI that misclassified them as being overweight when their body-fat levels were actually normal (Ode et al. 2007).

In my counseling practice, I use BMI to determine who is too thin. If you have normal musculature, an appropriate BMI is 18.5 to 24.9. When an athlete's BMI is less than 18.5, I need to rule out the possibility of anorexia. To determine if you fit this underweight category, search the Web for "body mass index calculator" and you'll find a variety of tools to assess your BMI.

Body-Fat Measurements

When I counsel athletes who have a poor concept of an appropriate weight, I measure their body fat rather than rely on scales and height and weight charts. The fat measurement helps put in perspective the proportion of an athlete's body that is muscle, bone, essential fat, and excess fat. A scale provides a meaningless number because it doesn't indicate the composition of the pounds. Although some pounds are desirable muscle weight, others are less desirable fat weight. Obviously, the muscle weight contributes to top athletic performance in most sports. The fat weight is the bigger concern because excess fat can slow you down.

Believe me, judging from the tension that radiates from the body of a weight-conscious athlete, I believe that getting your body fat measured ranks high on the list of anxiety-provoking life experiences. This number unveils the truth. Hulky football players are often humbled to learn that 20 percent of their brawn is flab. Weight-conscious gymnasts are often thrilled to learn that they are leaner than they thought they were.

If you want to have your body fat measured, you'll certainly want to have it done correctly by a qualified health professional to eliminate any possibility of being told that you are fatter than you really are. Inaccurate readings can send people into a tizzy. If you later want to be remeasured, try to have it done by the same person using the same technique to ensure greater consistency.

When it comes to measuring body fat, no simple, inexpensive method is 100 percent accurate. Common methods, such as underwater weighing, air displacement, calipers, and electrical impedance, all have potential inaccuracies. The following information evaluates these options to help you decide the best way to estimate your ideal weight should you want to quantify the fats of life.

Keep in mind that body-fat measurements should include a conversation about an appropriate weight for your body. If you are far leaner than other members of your genetic family but still have a higher percentage of fat than you desire, you may already be lean for your body. For example, a 5-foot, 6-inch (168 centimeter) walker lost 50 pounds (23 kilograms), from 200 to 150 (91 to 68 kilograms) and wanted to reach a seemingly appropriate weight goal of 130 pounds (59 kilograms). Because she couldn't seem to lose beyond 150 pounds without severely restricting her intake, I measured her body fat. She was 28 percent fat, at the higher end of average but far leaner than anyone else in her family. I suggested that she be at peace with this healthier weight and remember that she was currently thin for her body.

Underwater Weighing

Underwater weighing traditionally has been considered the most accurate method for determining body fat. With underwater weighing, the subject exhales all the air in his or her lungs and then is weighed while submerged in a tank of water. Despite popular belief, this technique does not measure body fat. Instead, it measures body density, which translates mathematically into percent fat. During the translation, however, significant error can creep into the picture. The equations for translating density into fat are most appropriate for the standard male. This excludes many thin runners and muscular bodybuilders. The same equations can be inappropriately used for girls on the high school swim team, 50-year-old marathoners, and professional football players.

Body density differs among all types of athletes, and age, gender, and race affect it. Children and senior citizens differ from each other in body density. The anorexic ballerina with osteoporotic, low-density bones is far different from the standard male and may receive an inaccurate estimate of body-fat percentage unless the difference in density is accounted for using a population-specific equation.

Errors with underwater weighing also stem from the inexperience of the person being weighed. If you've never been submerged into a weighing tank, you are likely to be nervous and may not completely exhale all the air in your lungs before going under the water. This will affect the density reading. Exercise physiologists have estimated that as little as 2 cups (a half liter) of air can affect body-fat measurements by as much as 3 to 5 percent. Intestinal gas can also disrupt the accuracy, as can poorly calibrated equipment. Many portable underwater weighing systems (the kinds that show up at road races, health fairs, and runners'

expos) may lack the precision of a weighing system used in a research laboratory.

Bod Pod

The Bod Pod uses a method similar to underwater weighing, except that the body displaces air instead of water. The Bod Pod is a podlike chamber with a top that swings open and a seat inside. The person sits inside, scantily clad. (Standard clothing takes up space and alters the reading, so the person should wear spandex clothing and a bathing cap). The technician closes the top of the Bod Pod and then takes air-pressure measurements that determine body volume from air displacement. These measurements are then translated into percent body fat, using a principle similar to underwater weighing. The accuracy is similar to that of underwater weighing; they agree within 1 percent (Fields, Goran, and McCrory 2002). Because the Bod Pod is quick, comfortable, easy, and less stressful than the underwater weighing method, it has become popular in health clubs, athletic departments at universities, and research settings.

Skinfold Calipers

Skinfold calipers are more convenient and less sensational than other methods of body fat measurement. The calipers are large pinchers that measure the thickness of the fat layer on specific body sites. Skinfold calipers are the most accurate of affordable ways for consumers to measure body fat (Peterson et al. 2007). However, health professionals well trained in the technique are the most qualified to use this method. Active people often obtain their measurements from students or novice technicians who may be using imprecise or poorly calibrated calipers at crowded health fairs or fitness events. A hasty measurement an inch above or below the established pinch point can add 5 to 15 millimeters of fat to the measurement. Those little millimeters can translate inaccurately into a high body-fat reading.

Even accurate measurements commonly translate into erroneous information because of inappropriate conversion equations. To be most accurate, the measurements from a runner, wrestler, bodybuilder, or gymnast should be plugged into sport-specific conversion equations. Such equations are seldom used for the average athlete.

The accuracy of body-fat measurements using calipers depends on the precision of the technician, the accuracy of the caliper, and the appropriateness of the conversion equations. Repeated measurements by different technicians using different calipers and different equations can yield widely different results.

Skinfold caliper measurements are best used to measure changes in body fatness. I often record on a monthly basis the measurements of people losing a significant amount of weight through regular exercise. By comparing the numbers (either as measurements in millimeters or converted into percent fat), the dieters can monitor changes. People recovering from anorexia may appreciate periodic skinfold measurements as a way to see that they are rebuilding muscle, not just gaining fat. This use of calipers may not give a 100 percent accurate picture, but it shows trends, particularly when the same technician measures the person each time, using the same calipers and same conversion equations.

Bioelectrical Impedance

Bioelectrical impedance analysis (BIA) measures body composition using a computerized system that sends an imperceptible electrical current through the body. The amount of water in the body affects the opposition to the flow of the current (impedance). Because water is found only in fat-free tissue, the current flow can be translated into percent body fat. As a result, it's relatively accurate if you are hydrated appropriately, but for sweaty athletes it is often less accurate than skinfold calipers.

Measuring body composition by bioelectrical impedance is a simple procedure that takes just minutes to perform. The whole-body machine (with electrodes attached to the wrists and ankles) is portable, easy to use, and popular at road races and health fairs. Other models that assess regional body composition come in the form of scales (leg to leg, such as the Tanita scale) and the handheld Omron model (arm to arm). Consumers who buy bioelectrical impedance scales should know that leg-to-leg measurements tend to be more accurate than hand-to-hand measurements.

Although it is a popular method, estimating body fatness by electrical impedance can be problematic, particularly among athletes. Because of the nature of the conversion equations, the body fatness of lean athletes is sometimes overestimated, and the fatness of overweight people is sometimes underestimated. If you measure yourself after you exercise, you'll likely have a lower percentage of fat compared with the preexercise measurement because hydration affects the reading (Demura et al. 2002). You will get an inaccurate reading if you are dehydrated (as often happens with wrestlers or in weight-class sports). Don't bother to be measured after hard exercise or after you've had any alcoholic beverages. As one of my clients reported, "I can be anywhere between 9 and 14 percent body fat, depending on when I use my Tanita scale."

Other factors that may affect the accuracy of the measurement include ethnic background, premenstrual bloat, food in the stomach, and carbohydrate-loaded muscles (water is stored along with the carbohydrate). The calculations are based on the assumption that the standard person is 73 percent water. Research has shown that young people tend to be 77 percent water and older folks 71 percent. If you are improperly positioned during the test (say, with part of your arms touching your body), you will also get an inaccurate reading. This error can easily happen in crowded exhibitions.

With the development of new sport-specific equations, accuracy is improving. Testing of the Omron handheld model indicates that it gives a reasonably accurate (within 3.5 percent) measurement 65 percent of the time with women and 70 percent of the time with men (Gibson, Heyward, and Mermier 2000).

What's the Use?

Until researchers find the definitive method to measure body fat, here's my advice. Consider body-fat measurement as a comparative tool to reflect changes in your body as you lose fat, gain muscle, shape up, and slim down. Don't expect more accuracy than is possible. The standard error is plus or minus 3 percent. Hence, if you are measured at 15 percent, you might be 12 percent or 18 percent. That doesn't take into account another 3 percent biological error because of individual variations in body fatness.

Just as weighing yourself on different scales results in different pound values, having your body fat measured by different people using different methods also results in different body-fat numbers. In a study done on 57 white male college students, their body fat ranged from 12.5 percent to 18.5 percent, depending on the method. This demonstrates the significant variability that occurs even under scientific conditions (Stout et al. 1994).

Your best bet is to see how the measurements change over time. Have the same person measure you at regular intervals to help you assess trends in your body-fat changes. But the measurements likely tell you nothing you didn't already know from looking at yourself in the mirror or from the fit of your clothing.

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