How much should I weigh?

A lot of us get really hung up on that number on the scale. But weight doesn’t tell you much about your health and fitness status, or even how you look! A crucial part of determining how much you should weigh has to do with what makes up that weight. For example, is your weight made up of a healthy ratio of muscle, bone, and fat? Knowing this can help you interpret your scale reading.

Body Mass Index
The body mass index (BMI) is a screening tool to assess weight status. You can use the calculation below to determine your BMI. Keep in mind that BMI is only based on height and weight; it does not take into consideration your body composition or genetics. A healthy weight for you may be higher than the BMI standards. Your eating habits, physical activity patterns, other lifestyle choices, body composition, and genetics are more important than any number on the scale in determining what weight is right for you. Use BMI as a rough indicator, and consult a health professional to help you determine what weight is right for you.

How do you calculate BMI?
BMI is calculated by the following formula: weight in kg / height in m2. If you're not familiar with kilogram and meter measurements, follow the steps below to calculate your BMI.

Step 1. Take your weight (in pounds) x 703
Step 2. Divide that number by your height (in inches)
Step 3: Divide that number by your height (in inches) again

Example: Woman who is 5’3” and weighs 135 lb.
Step 1. 135 lb. x 703 = 94,905
Step 2. 94,905 / 63” = 1506
Step 3. 1506 / 63” = 23.9
BMI = 23.9

BMI Standards
Underweight < 18.5
Healthy weight 18.5-24.9
Overweight 25.0-29.9
Obese I 30.0-34.9
Obese II 35.0-39.9
Obese III 40+

Body Fat
Body composition is a better indicator of your health and fitness status than body weight, but it is still not perfect. Your genes determine your body type. Some body types carry more fat than others--no matter what you eat or how much you exercise. Percent body fat does not necessarily tell you how healthy or fit you are, or tell you how you look. There are large-framed students who have a higher percentage of body fat who train for triathlons, exercising several times a week and eating a healthy balanced diet. Other students may be ultra-thin and have a lower percentage of body fat, but don’t consume adequate calories or nutrients, lack physical endurance and strength, and don’t look healthy or fit.

Unlike BMI, there is no one universally accepted set of body fat standards. As a result, you may see many different reference ranges from various fitness organizations, fitness magazines, and gyms. Not all of these reference ranges are based on research or take into account such things as genetics. As a result, many ranges are too narrow to reflect the diversity of healthy and fit bodies. A normal and healthy percentage of body fat varies substantially, and charts and graphs should not be regarded as the “end-all-be-all” of what is healthy and normal for you personally.

Body Fat Standards
The American College of Sport’s Medicine developed the following reference ranges based on research.

• “Health standards” reflect the percent of body fat that generally does not increase your risk for health problems. Excessive body fat, especially around the abdomen, can increase your risk for high blood pressure, diabetes, osteoarthritis, and heart disease. Young men who have greater than 22% body fat and young women who have greater than 35% body fat may be at greater risk for these health problems, independent of their eating, activity, and other lifestyle behaviors.

• “Fitness standards” reflect the percent of body fat that generally results from greater physical training. A greater percentage of muscle and lower percentage of fat may improve strength, speed, endurance, and agility. However, dropping below 16% body fat for women and 5% body fat for men DOES NOT further increase your athletic performance or level of fitness. Instead, too low body fat can actually impair your physical health and performance. Men and women need a certain amount of body fat to insulate vital organs, regulate body temperature, and ensure adequate production of sex hormones. In particular, women who restrict calories and exercise excessively may have a very low percentage of body fat and consequently have very low estrogen levels and stop menstruating. Because estrogen keeps women’s bones strong, women who stop menstruating are at much greater risk for stress fractures and a debilitating bone-thinning disease called osteoporosis.

How do you measure body fat?
There are many methods for determining body composition, including skin fold measures, bioelectrical impedance, and underwater weighing.

Which method is best? The accuracy of each method can be highly variable depending on the skill of the person doing the measurement, whether the person being measured is well hydrated or dehydrated, how good the equipment is, and/or the reference tables used. Even the best techniques have an error of at least 3%, plus or minus. That means that if your body fat is tested at 20%, it could really be anywhere between 17 and 23%. You can get one reading today and a different one tomorrow.

To accurately monitor changes in body fat over time, be sure to use the same technique with the same person under the same conditions each time you take a measurement. If you switch to a different technique, you may get different results for any number of reasons having nothing to do with real changes in your body composition. It takes several months to see any true changes in body composition, so there’s no need to repeat testing more than once every 3 months.

Body Types
Each one of us inherits a specific body type. Even though the media would have us think otherwise, there are really many healthy and normal body types. For ease of reference, body types have been categorized into three main types, and those types have been further categorized as blends of the three main types. Each body type has advantages over the others for certain activities, but a person with any body type can be healthy and fit and look great!

Ectomorphs are generally tall and thin and have long arms and legs. These people have difficulty gaining weight and muscle no matter how much they eat or how hard they weight train. They have the body type you tend to see in ballet dancers, runway models, long-distance runners, and basketball players. A very small proportion of the population has this type of body.

Mesomorphs are generally muscular, shorter, and have stocky arms and legs. These people are strong and tend to gain muscle mass when they do strength training. They may find it difficult to lose weight, but they excel in power sports like soccer, softball, vaulting in gymnastics, sprinting events in track and field.

Endomorphs are generally shaped like apples or pears and carry more body fat. Their bodies resist losing weight and body fat no matter how restrictive they are with their eating. In fact, the more they “diet,” the more their metabolisms slow down to resist weight loss. These people are better able to handle long periods of starvation and famine (which was a benefit to our ancestors). Sports they excel at are distance swimming, field events, and weight lifting.

If you don’t think you fit into any of these, don’t worry. Many of us fall somewhere in between. The important thing to know is that there are many body types, and all of these types are normal.

The Media’s “Ideal” Body
The media sets unrealistic standards for what body weight and appearance is considered desirable.

Young girls believe that Barbie is how a woman is supposed to look (i.e. no fat anywhere on your body, but large breasts). But, if Barbie were a real person, she would be 5’9” tall and weigh 110 pounds, only 76% of her healthy weight. Her measurements would be 39-18-33, and she likely would not be able to menstruate due to being underweight.

Similarly, young boys are given the impression that men are supposed to have muscles bulging all over their bodies. Take a look at their plastic action-figures like GI Joe Extreme. If GI Joe Extreme were life-size, he would have a 55 inch chest and a 27 inch bicep. In other words, his bicep would be almost as big as his waist and bigger than most competitive body builders.’

The media’s portrayal of what is desirable and normal keeps getting thinner and thinner for women and more muscular and cut for men. For example, 25 yrs. ago the average female model weighed 8% less than the average American woman. Currently, the average female model weighs 23% less than the average American woman. Similar trends are being seen with men. In the past 25 years, the average playgirl centerfold man has shed about 12 lbs. of fat, while putting on approximately 27 lb. of muscle.

In reality, only about 5-10% of women have the ultra-long and thin, model body-type. Yet that is often what most women aspire to be. Similarly, boys see a body ideal that is impossible to achieve without resorting to extreme measures such as taking anabolic steroids. There is a physiologically limit to how much muscle a man’s body can attain naturally, given his height and body fat percentage, just as there is a limit to how thin a woman can look due to her body type.

Another thing to keep in mind is that physical attractiveness is about more than body shape and size. It also matters how you present yourself (sometimes a good hair cut or bright smile can make a big difference), or if you are a fun person to be with, just as examples. People who come across as too perfect are often intimidating. It’s important to know that you can do other things to improve your appearance without focusing exclusively on your body shape and size.

What can you do to achieve your personal best?

• Realize that you cannot change your body type, and try not to compare yourself to others. You are who you are, and no one else can be you!

• Invest time and money in yourself in ways that make you feel your best. Examples include getting a manicure or massage, buying new clothes or fitness equipment (like walking shoes, gym bag, resistance bands, free weights, etc.), enrolling in a yoga, dance, or martial arts class. Avoid spending money on diet products.

• If you weigh yourself, only do so once a week, and be sure to choose the same time of day and wear the same amount of clothes each time. It’s normal for weight to fluctuate by a couple of pounds (up or down) daily or even at different times in the same day, due to fluid shifts or how much you’ve recently eaten, drunk, perspired, or gone to the bathroom. If you feel the need to measure your body fat percentage, only do so once every 3 months. Choose the same method and measurer, and remember that there is at least a 3% margin of error with even the best methods.

• Learn to fuel your body for optimal energy, fitness, and health! Enroll in a nutrition class or read the other sections of this web site to find out how well your current eating plan meets your needs.

• Move and enjoy your body, not because you have to, but because it makes you feel good! Go for a walk, a swim, or a bike ride, or dance to boost your energy, mood, and cardiovascular health. Do yoga, tai chi, or stretching to relax and improve your flexibility. Use weights, resistance bands, or your own body weight to build muscular strength and endurance.

• Reduce stress. Learning to manage stress can sometimes influence how you feel about your body and weight. You might be surprised how reducing stress in other parts of your life can put your whole life in perspective!

• Click here for more info on body image.

Sheri Barke, MPH, RD
COC, Student Health & Wellness Center
Rev. 2005