The Body Mass Index (BMI) serves as an estimate of body composition (the ratio of fat to muscle and bone) based on your height and weight. According to the National Institutes of Health, the BMI is a reliable indicator of total body fat, which is related to the risk of disease and death. Being overweight or obese increases the risk of hypertension, heart disease, stroke, diabetes and some cancers.
Deaths from obesity-related causes in the U.S. are now the second-leading cause of death after smoking, accounting for more than 16 percent of all deaths. The Body Mass Index is valid for both men and women 18 years of age or older, but may overestimate body fat in people who have a muscular build (bodybuilders) and may underestimate body fat in people who have lost muscle mass (pot-bellied people with spindly legs). The BMI is the ratio of the weight to the height squared; it is calculated by dividing the weight in kilograms by the height in meters squared (BMI = weight / height2).
|Underweight||BMI less than 18.5|
|Normal weight||BMI 18.5 to 24.9|
|Overweight||BMI 25 to 29.9|
|Obese||BMI 30 or greater|
|Morbidly Obese||BMI 40 or greater|
|Enter your height and weight and click the "Compute BMI" button.|
The Body Mass Index provides a rough estimate of the proportions of the human body. Thin people usually have a smaller BMI than fat people. However, an "ideal figure" is judged by aesthetics and it has nothing to do with any medical criteria about fitness or health. People find beauty in the complete spectrum of human body types, from emaciated supermodels who eat inadequate diets to grotesquely muscular body builders who use steroids. Artists and sculptors through the ages have studied the proportions of the human body looking for ideal figures. Leonardo da Vinci's Vitruvian Man, drawn around the year 1490, is a study of the proportions of the human body. It shows the pubis as the center of a square with sides equal to the man's height, and the navel as the center of a circle touched by the man's outstretched arms and legs. Ideally, for both men and non-pregnant women, the size of the waist should be smaller than the measurement around the hips. Also, the Waist-to-Height ratio should be less than 0.5. By measuring the Vitruvian man, we can calculate his Waist-to-Height ratio as 0.47. (The height is 80 mm, the waist diameter is 12 mm, and assuming a circular waist, the waist circumference would be approximately 37.7 mm). If the Vitruvian man had a height of 5 feet, 8 inches (172 cm), his waist size would be 32 inches (81 cm). Gymnasts and modern-day boxers who must optimize agility, strength, and stamina for a specific weight range have bodies that resemble the Vitruvian Man more than than they resemble muscular body builders.
Our modern society glamorizes actresses like Marilyn Monroe as prototypes of ideal feminine beauty and sensuality. By the way, Marilyn Monroe was 5 feet, 6 inches tall and weighed 128 pounds (BMI 20.7). Most advertisements show pictures of skinny fashion models with bony bodies in daring poses that suggest confidence, seductiveness, and success. These idealized women either tend to have small waists and large breasts in proportion to their height or are simply flat-chested and bony. Average women who are trying to become physically fit are often frustrated that no amount of dieting or exercise can give them one of these divergent "ideal" body types, specially after bearing children. Many perfectly healthy women finally resort to surgical procedures such as breast enlargement or liposuction to try to overcome the negative images about their own body. A more realistic standard of ideal feminine proportions is the statue of Venus de Milo, sculptured around 130 B.C. She has B-cup breasts, and her Waist-to-Height ratio is 0.5, even though she is not standing straight in this pose. Waist-to-Height ratios greater than 0.5 are indicative of intra-abdominal fat for both men and women and are associated with a greater risk of cardiovascular disease. Waist-to-Height ratios greater than 0.55 also increase the risk of developing type 2 diabetes.
Because over 60% of the population in the United States is overweight or obese, two classifications of body shapes have been introduced for overweight people. The "pear" body shape describes people who store fat below the waistline on their hips, thighs, and buttocks as opposed to their stomachs and mid-sections. This is more typical of women. The "apple" body shape is characterized by a wide torso and large abdomen. Men who have an apple body shape are said to have a "beer belly", a "pot belly", or "love handles". The body is classified as pear-shaped if the waist-to-hip ratio, i.e., the size of the waist divided by the size of the hips, is 0.80 or lower. If the ratio is higher than 0.80, the body is classified as apple-shaped. Apple-shaped people seem to have a greater chance of having heart attacks and developing hardening of the arteries, high blood pressure and diabetes, whereas pear-shaped people seem to have a lower risk of developing these conditions.
Abdominal obesity, diabetes, high cholesterol, and high blood pressure are the most dangerous heart attack risk factors. The combination of these conditions is called metabolic syndrome. People with metabolic syndrome are two times more likely to die of a heart attack or stroke than people without the syndrome.
When evaluating diet advertisements, keep in mind that the Federal Trade Commission has determined that any product claims are false if they state that you can lose more than two pounds per week for more than four weeks without diet and exercise.