Written by Marsha Seidelman, M.D.
July 14, 2015
Jody Miller’s article published today describes how repeated weight measurement may be counterproductive for some people. Another number, the BMI, is often used as a way to evaluate body weight relative to height; it is the ratio of weight (in kilograms) to height (in meters) squared.
Your BMI can be determined from a table or a calculator :
http://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm
A BMI of 19-25 kg/m2 is generally considered to be good, with over 25 being classified as overweight, over 30 being obese and over 40 massively obese.
A higher BMI is generally associated with obesity and risk of death from all causes and specifically from heart disease. However, a higher BMI in someone who weighs more because (s)he is muscular, would NOT represent a high risk. Each square inch of muscle weighs more than a square inch of fat tissue.
One of the drawbacks of BMI is that it is based only on weight and height, not on body build. Someone with a larger bone structure would be expected to weigh more (and have a higher BMI) than someone of the same height with a petite build, based on heavier bones and a broader build – more space to fill, so to speak. This is not necessarily less healthy, just different. Here are great visuals showing how the BMI does NOT account for different body types.
So the BMI is easy to measure, and provides a better estimate of total body fat compared with body weight alone, but IT doesn’t tell the whole story either.
Measurement of the waist circumference or waist-to-hip ratio adds further information to the BMI regarding health risk. When the waist increases, it can be assumed to be due to fat accumulation, not to muscle bulk. Excess fat around the waist is felt to be metabolically active, contributing to heart disease.
To check your waist circumference properly, wrap a tape measure around your middle, just above your hipbones. Measure your waist just after you breathe out.
A waist circumference of ≥40 inches for men and ≥35 inches for women is considered elevated and indicates increased health risk. This situation, also called abdominal or central obesity, leads to increased risk for heart disease, diabetes, high blood pressure, high cholesterol, and nonalcoholic fatty liver disease.
A high waist-to-hip ratio further helps to classify people as ‘apple’ shaped – a large waist with higher health risks, or ‘pear-shaped – a lower ratio, due to a thinner waist. The female, or pear shape, with more weight around the hips, doesn’t raise the risk for heart disease the way abdominal obesity does.
Another measurement you might see used at gyms is body fat percent. This can be estimated by using calipers to pinch high fat areas, such as the ones dangling near the triceps on many people, especially women. However, this way of measuring body fat is inaccurate, as are many of the ‘body fat’ scales sold for this purpose. The most accurate measurement involves going into a pool of water, and so is very inconvenient. A middle ground might be using a calculator, as shown here, with multiiple data points. The author also discusses preferred levels of body fat.
Whether assessed by scale weight, BMI, waist circumference, waist-to-hip ratio, or body fat percent, overweight or obesity is usually due to too little activity in relation to too many calories. However, if you are having difficulty losing weight, your physician will likely choose to check your thyroid function, blood chemistries or other tests as appropriate to look for additional causes. Some medications may add to weight gain as well, including commonly used diabetic medications and anti-depressants. That’s not to say they shouldn’t be used, it’s just to recognize that weight gain may be a side effect.
If none of these factors create an opportunity for weight loss, then we’re back to the good old fashioned healthy Mediterranean style low calorie diet and 30 minutes of cardio exercise most days of the week, as the healthiest weight loss program. I’d like to echo what Jody said, in that the goal is a healthier fitter body, not a particular number on the scale.
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