Measuring a person’s body fat percentage can be difficult, therefore, other methods are relied on to diagnose obesity. Two widely used methods are weight-for-height tables and body mass index (BMI). While both measurements have their limitations, they are reasonable indicators that someone may have a weight problem. The calculations are easy, and no special equipment is required.

Most people are familiar with weight-for-height tables. Doctors and nurses (and many others) have used these tables for decades to determine if someone is overweight. The tables usually have a range of acceptable weights for a person of a given height.

One small problem with using weight-for-height tables is that doctors disagree over which is the best table to use. Several versions are available. Many have different weight ranges, and some tables account for a person’s frame size, age and sex, while other tables do not.

A grave limitation of all weight-for-height tables is that they do not distinguish between excess fat and muscle. A very muscular person may appear obese, according to the tables, when he or she in fact is not.

What is the body mass index (BMI)?

The body mass index (BMI) is a new term to most people. However, it is now the measurement of choice for many physicians and researchers studying obesity.

The BMI uses a mathematical formula that accounts for both a person’s weight and height. The BMI equals a person’s weight in kilograms divided by height in meters squared (BMI=kg/m2).

The BMI measurement however, poses some of the same problems as the weight-for-height tables. Not everyone agrees on the cutoff points for “healthy” versus “unhealthy” BMI ranges. BMI also does not provide information on a person’s percentage of body fat. However, like the weight-for-height table, BMI is a useful general guideline and is a good estimator of body fat for most adults between the ages of 19 and 70 years of age. However, it may not be an accurate measurement of body fat for body builders, certain athletes, and pregnant women.

It is important to understand what “healthy weight” means. Healthy weight is defined as a body mass index (BMI) equal to or greater than 19 and less than 25 among all people aged 20 or over. Generally, obesity is defined as a body mass index (BMI) equal to or greater than 30, which approximates 30 pounds of excess weight. Excess weight also places people at risk of developing serious health problems.

The table below has already done the math and metric conversions. To use the table, find the appropriate height in the left-hand column. Move across the row to the given weight. The number at the top of the column is the BMI for that height and weight.

 BMI  (kg/m2) 19 20 21 22 23 24 25 26 27 28 29 30 35 40 Height(in.) Weight (lb.) 58 91 96 100 105 110 115 119 124 129 134 138 143 167 191 59 94 99 104 109 114 119 124 128 133 138 143 148 173 198 60 97 102 107 112 118 123 128 133 138 143 148 153 179 204 61 100 106 111 116 122 127 132 137 143 148 153 158 185 211 62 104 109 115 120 126 131 136 142 147 153 158 164 191 218 63 107 113 118 124 130 135 141 146 152 158 163 169 197 225 64 110 116 122 128 134 140 145 151 157 163 169 174 204 232 65 114 120 126 132 138 144 150 156 162 168 174 180 210 240 66 118 124 130 136 142 148 155 161 167 173 179 186 216 247 67 121 127 134 140 146 153 159 166 172 178 185 191 223 255 68 125 131 138 144 151 158 164 171 177 184 190 197 230 262 69 128 135 142 149 155 162 169 176 182 189 196 203 236 270 70 132 139 146 153 160 167 174 181 188 195 202 207 243 278 71 136 143 150 157 165 172 179 186 193 200 208 215 250 286 72 140 147 154 162 169 177 184 191 199 206 213 221 258 294 73 144 151 159 166 174 182 189 197 204 212 219 227 265 302 74 148 155 163 171 179 186 194 202 210 218 225 233 272 311 75 152 160 168 176 184 192 200 208 216 224 232 240 279 319 76 156 164 172 180 189 197 205 213 221 230 238 246 287 328

Body weight in pounds according to height and body mass index.

Below is a table identifying the risk of associated disease according to BMI and waist size.

 BMI Category Waist less than or equal to   40 in. (men) or 35 in. (women) Waist greater than 40 in.  (men) or 35 in. (women) 18.5 or less Underweight N/A N/A 18.5 - 24.9 Normal N/A N/A 25.0 - 29.9 Overweight Increased Risk High Risk 30.0 - 34.9 Obese High Risk Very High Risk 35.0 - 39.9 Obese Very High Risk Very High Risk 40 or greater Extremely Obese Extremely High Risk Extremely High Risk

Provided by ArmMed Media
Revision date: July 6, 2011
Last revised: by Sebastian Scheller, MD, ScD