Are You at a Healthy Weight? Learning your body mass index, or BMI, is a quick way to see whether you're at a healthy weight for your height. What is BMI? Finding out your body mass index (BMI) is a quick way to figure out if your weight is healthy for your height. Your BMI value is more useful for predicting your health risks than your weight alone, but it's even more useful to treat it as one of many factors that influences your health, including total body fat, waist circumference and waist-to-hip ratio. How is it calculated? Body mass index is calculated by this formula, developed by the Belgian statistician Adolphe Quetelet in the nineteenth century: Weight in kilograms = BMI(Height in meters)² Since Americans measure weight and height in pounds and feet instead of kilograms and meters, the converted formula looks like this: Weight in pounds x 704.5 = BMI(Height in inches) ² If you don't feel like pulling out a calculator, you can use our BMI calculator, which will be coming soon on this page, to figure out your BMI. What does it mean? Quetelet decided that if the result of the calculation was greater than 30, it signaled obesity. This is still a good rule of thumb, but over the years nutritionists have developed more refined ways to interpret BMI values. For example, different BMI values can mean you are underweight, ideal weight, slightly overweight or obese, and these BMI ranges are slightly different for men and women. Range......................Women..............Men Underweight............ Less than 19.1 ...Less than 20.7 Ideal weight............ 19.1 to 25.8 .... 20.7 to 26.4 Marginally overweight... 25.8 to 27.3 .... 26.4 to 27.8 Overweight ............. 27.3 to 32.2 .... 27.8 to 31.1 Very overweight or obese 32.3 to 44.8 .... 31.1 to 45.4 Extremely obese ........More than 44.8 ... More than 45.4 (Source: Understanding Nutrition by Whitney and Rolfes) In June, 1998, the National Heart, Lung, and Blood Institute and the National Institute of Diabetes and Digestive and Kidney Diseases issued controversial new guidelines for clinicians to identify overweight people. These guidelines use the same ranges of numbers for men and women, and place many more people in the "overweight" category than previous estimates. Underweight ...... Less than 18.5 Normal ........... 18.5 to 24.5 Overweight ....... 25.0 to 29.9 Obese: class I ... 30.0 to 34.9 class II ... 35 to 39.9 Extremely obese ...More than 40.0 (Source: NIH Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, June 1998) What are its limitations? Using BMI to predict overweight still has its limitations, though. It doesn't take frame size into account, so people with stockier builds may be considered overweight even if they don't have a lot of body fat. Tests that physically measure body fat and distribution are better than BMI at telling if you are overweight. A skinfold measure, for example, uses a instrument called calipers to measure the thickness of the fat layer on your arm or stomach. A bioelectrical impedance test how easily electricity travels through your body (fatty tissue slows down the current) to estimate what percentage of the body is fat. These tests involve a physical measurement by a trained technician at a gym or doctor's office. Also, BMI is not a good predictor of overweight for these groups of people: • Children and teens, because BMI ranges are based on adult heights • Competitive athletes and bodybuilders, because heavier muscle weight may skew the results • Pregnant or nursing women, because they need more fat reserves than usual • People over 65, because even BMI values of 29 do not appear to be unhealthy at this age, and may even be a useful energy reserve in case of illness To schedule a telephone consultation or an appointment at our office in Olean, N.Y. call (716) 373-5636.