Body mass index (BMI) and the right weight for my height?

(1) Alice,

A friend and I were discussing this. We both try to stay healthy by eating well (high fiber, low fat, lots of veggies, fruit, etc.) and living an active enough lifestyle (hiking, rock climbing, biking, etc.) that we stay in shape. The question we have, then, is what the current "rules" are for appropriate weight/height ratios? Or are such measurements now thrown out in favor of body fat percentage measurements? She's 5'1" and I'm 6'1" and we're curious what the medical rule of thumb would be for how much each of us "should" weigh...mostly because we're wondering if it takes into account things like muscle mass. What would the current medical/health industry recommend each of us weigh? Are these numbers accepted or are they seen as not as important as they might have been 20 years ago. If you have actual numbers, we'd be curious to see that too. Thanks! I have a dinner riding on this!

— Curious

(2) Dear Alice,

Could you clarify the Body Mass Index deal? According to one BMI chart, I am "slightly overweight" because I am 5' 5-1/2" tall and weigh 160 lb. I am also very muscular and have a large frame. The lower BMI readings are labeled "ideal," but I've heard muscle weighs more than fat, so if the chart does not include the muscle factor, is it basically saying that it's "ideal" NOT to have extra muscle? I look slender and have never been told by a doctor to lose weight. I'm a twenty-four-year-old female, lacto-ovo-vegetarian, and get lots of exercise, including walking and frequent "sweaty" workouts.

— Scales

Dear Curious and Scales,

If you're trying to find your "ideal" weight, you may not want to bet your bottom dollar on a height-weight ratio, or any one indicator for that matter. There are any number of factors that impact a person’s weight, making it difficult to determine someone’s ideal numbers. With that being said, body mass index (BMI) and waist circumference are two measures that, when higher, may indicate an increased risk of certain health issues. However, no matter where the scale points, maintaining a balanced diet and regular physical activity are two signs that you're both on the right track to fitness and overall good health.

One popular way to compare height and weight is BMI. This measure essentially uses a math equation to create a ratio, similar to the older height-weight charts. Lower scores indicate a person is likely on the lean side, while higher scores may mean they’re carrying excess weight. While BMI provides a range for "healthy" and "unhealthy" weight, it may also hide key differences in body composition. For example, BMI scores don't account for the fact a given volume of muscle weighs more than the same volume of fat (just as you noted, Scales). This means a person who has a lot of muscle may fall within the “unhealthy” range even though other indicators show they’re healthy. On the flip side, someone who carries more fat and minimal muscle mass may fall within the "healthy" range. What’s more, BMI says nothing about the distribution of fat throughout your body (more on that later). For a full description, check out About BMI for Adults from the Centers for Disease Control and Prevention (CDC) website.

Another helpful way to assess body size requires that you break out some measuring tape to determine your waist size. As it turns out, not all fat is created equal. Packing extra pounds around the belly (as opposed to the hips) carries more health risks than fat in other areas of the body. According to the National Institutes of Health (NIH), the chances of developing heart disease, hypertension, and type 2 diabetes increases when waist circumference exceeds 35 inches for non-pregnant folks who are assigned female at birth or 40 inches for people assigned male at birth.

Measurements aside, yet another way to define "healthy" weight is by whatever size your body settles at naturally when you follow a balanced diet and get the recommended amounts of physical activity. Take a moment to think about all the things you want and need to do. Are you able to do them without feeling overexerted? How about any family history of illness related to weight? Do you feel comfortable and confident in who you are/what your body looks like regardless of the charts you’ve seen? Your answers to these questions may be more helpful that using the math and charts associated with a simple BMI calculation. 

If you want to explore these topics further, talking with a registered dietitian might also help; they can assess your eating patterns, activity levels, and body size to help determine what a healthy weight looks like for you. People come in many shapes and sizes, so an ideal weight for any one person may be different than another.

Weight and body size are key health indicators, but banking on numbers alone may not give you a complete picture of your overall fitness. Hopefully this information helps to settle the score!

Last updated Mar 31, 2017
Originally published Nov 01, 1993

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