BMI - Body Mass Index

Weighing on Scale
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Body Mass Index (BMI) is a relationship between weight and height that is associated with body fat and health risks. Research has identified the health risks associated with a wide range of BMIs (both high and low values.)

Calculate Your BMI - Body Mass Index

The National Institutes of Health lists these BMI categories:

  • Underweight: BMI less than 18.5
  • Normal weight: BMI between 18.5 and 24.9
  • Overweight: BMI between 25 and 29.9
  • Obese: BMI of 30 or greater.

Further, obesity is classed by increasing BMI:

  • Obesity Class I: BMI 30.0–34.9 -  High health risks, very high if you have an increased waist circumference.(over 40 inches for men and over 35 inches for women).
  • Obesity Class II: BMI 35.0–39.9 - Very high health risks
  • Obesity Class III - Extreme Obesity: BMI 40 and above. Extremely high health risks.

The specific health risks for these classes are increased incidence of  type 2 diabetes, hypertension, and cardiovascular disease.

BMI Ranges by Weight in Pounds

 

BMI <18.5

BMI 18.5-24.9

BMI 25-29.9

BMI 30-34.9

BMI 35-39.9

BMI >40

Height

Underweight

Normal Weight

Overweight

Obese Class I

Obese Class II

Obese Class III

4'10"

<88 lb.

88-119 lb.

119-143 lb.

143-167 lb.

167-190 lb.

>191 lb.

4'11"

<91

91-123

124-148

148-172

173-197

>198

5'0"

<94

94-127

128-153

153-178

179-204

>204

5'1"

<97

97-131

132-158

158-184

185-211

>211

5'2"

<101

101-136

136-163

164-190

191-218

>218

5'3"

<104

104-140

141-168

169-197

197-225

>225

5'4"

<107

107-145

145-174

174-203

204-232

>232

5'5"

<111

111-149

150-179

180-209

210-239

>240

5'6"

<114

114-154

155-185

186-216

216-247

>247

5'7"

<118

118-158

159-190

191-222

223-254

>255

5'8"

<121

121-163

164-196

197-229

230-262

>262

5'9"

<125

125-168

169-202

203-236

236-270

>270

5'10"

<128

128-173

174-208

209-243

243-278

>278

5'11"

<132

132-178

179-214

215-250

250-286

>286

6'0"

<136

136-183

184-220

221-257

258-294

>294

6'1"

<140

140-188

189-226

227-264

265-302

>302

6'2"

<144

144-193

194-232

233-271

272-310

>311

6'3"

<148

148-199

200-239

240-279

279-319

>319

6'4"

<152

152-204

205-245

246-286

287-327

>328

BMI Tables: Look up your BMI based on your height in inches and weight in pounds.

Calculating BMI

The equation to calculate is BMI = body weight in kilograms/height in meters squared.

Because this equation uses metric numbers for height and weight, Americans usually prefer to use a calculator or look it up in a table based on inches and pounds rather than kilograms and meters.

If you want to do the math:

  • Take your weight in pounds and divide it by 2.2 to get your weight in kilograms.
  • Find your height in inches. One foot = 12 inches. Five feet = 60 inches. Six feet = 72 inches. Add in the inches you are above 5 foot or 6 foot to get your height in inches.
  • Divide your height in inches by 39.36. Now take that number and multiply it by itself to square it.
  • Now divide your weight in kilograms your height in meters squared.

Accuracy of BMI

BMI can be inaccurate in estimating body fat. Athletes with a very muscular build will have a BMI that overestimates body fat. They are leaner than their BMI indicates. On the opposite end, older people and others who have lost muscle may have higher body fat than their BMI indicates.

Health Risks by BMI and Waist Circumference

Measuring your waist is another indicator of health risk, as storing fat around your waist is associated with an increased risk of heart disease and diabetes. You can have a normal BMI and body weight but if your waist measurement is greater than 35 inches for women or greater than 40 inches for men, you will fall into the overweight or obese categories and have increased health risks.

Health risks in the overweight and obese classifications are raised by having two or more of these risk factors: high blood pressure, high LDL cholesterol, low HDL cholesterol, high triglycerides, high blood sugar, being physically inactive, smoking cigarettes, and having a family history of premature heart disease.

Losing weight can lower the health risks for those who are in the obese BMI range and for those who are in the overweight range and have two or more risk factors, according to the NIH. Losing weight reduces health risks, even losing just 5% to 10% of your weight. For a 200 pound person, that would be 10 to 20 pounds. For a 250 pound person, that would be 12.5 to 25 pounds.

Source:

Assessing Your Weight and Health Risk. National Heart, Lung and Blood Institute, National Institutes of Health.

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