Obesity is often defined by Body Mass Index' [BMI], a metric that is more useful when combined with others [to be discussed later]:
| BMI | Classification |
|---|---|
| < 18.5 | underweight |
| 18.5–24.9 | normal weight |
| 25.0–29.9 | overweight |
| 30.0–34.9 | class I obesity |
| 35.0–39.9 | class II obesity |
| ≥ 40.0 | class III obesity |
BMI = weight in kilograms / [height meters]2
BMI = weight in pounds x 703 / [height inches]2
BMI can be misleading, as it takes no account of muscle mass.
For example: Franco Columbu [photo below] in peak condition weighed 185 lbs at 5ft 5inches [BMI 30.7 > class I obesity!].
Franco had virtually Zero body fat. He was a world class body builder and renowned as one of the world's strongest men.
So you can see how BMI sometimes relates poorly to weight condition.
To get a better picture, we can use different metrics to help evaluate the weight condition.
Waist-hip ratio [WHR] is a good measure of weight condition, and health risk. More weight around the waist, compared with weight around the hips, is known to cause greater risk to health.
WHR is easy to measure: > hip girth at the widest part / waist girth at the belly button. | Male | Female | Health Risk Based on WHR |
| 0.95 or less | 0.80 or less | Low Risk |
| 0.96 - 1.0 | 0.81 - 0.85 | Moderate Risk |
| 1.0+ | 0.85+ | High Risk |
%PERCENT BODY FAT
In my opinion % body fat and WHR are better metrics for weight condition than is BMI.
Use the above diet calculator to find your % body fatFEMALE
| Age Yrs | Underfat | Healthy | Overweight | Obese |
| 20-40 | < 21% | 21-33% | 33-39% | 39%+ |
| 41-60 | < 23% | 23-35% | 35-40% | 40%+ |
| 61-79 | < 24% | 24-36% | 36-42% | 42%+ |
MALE
| Age Yrs | Underfat | Healthy | Overweight | Obese |
| 20-40 | <8% | 8-19% | 19-25% | 25%+ |
| 41-60 | <11% | 11-22% | 22-27% | 27%+ |
| 61-79 | <13% | 13-25% | 25-30% | 30%+ |
