Everyone has body fat. Humans need it for things as varied as extra storage for energy, heat insulation, and shock absorption/padding. Most Americans, however, have more than enough fat to cover these basic needs, since 2/3 of the country is considered overweight as of the latest 2004 census data.

Overweight is defined as an excess of body weight compared to set standards. This excess weight doesn't always come from fat; muscle, bone, and body water also contribute, and all of these variables must be taken into account when determining whether or not you're truly overweight.

Obesity is defined as having a body mass index (or BMI) greater than 30 kg/m2 - defined as your weight in kilograms divided by your height in meters squared. The BMI takes into account how much you weigh for your height.

While it's a useful measurement for most of us, it's not always an accurate assessment of obesity. For example, at the height of his body-building days, Arnold Schwarzenegger had a BMI 35 kg/m2, which would make him obese by BMI standards! His BMI was skewed by his muscle mass, which weighs twice as much as fat.

Morbid obesity means that a person is so overweight that his or her well-being and health are actually in jeopardy. It is defined in several different ways:

1. Weighing more than 100 pounds over your ideal body weight.
   Ideal body weight is determined by the Metropolitan Life Insurance table, and is based on mathematical formulas that Met Life uses to determine insurance risks.
2. A Body Mass Index (BMI) equal to or greater than 35 kg/m² in a person who has associated medical problems. These problems include high blood pressure, sleep apnea, or diabetes.
3. A Body Mass Index (BMI) equal to or greater than 40 kg/m² in a person who either does or does not have any other medical problems.

People who are morbidly obese are at a much higher risk (compared to individuals who are not overweight) of the following:

• premature death
• developing diabetes, high blood pressure and heart disease
• developing colon, breast, and uterine cancer
• developing premature arthritis and joint pain, causing limited mobility and activity.
• developing sleep apnea and pulmonary hypertension (which leads to heart failure).

It is estimated that over 400,000 people a year in the U.S. die of causes directly attributable to obesity. Learn more about the Treatment of obesity.

For people who are obese or morbidly obese, weight-loss surgery is often their last, best chance to regain a chance at leading a healthier, longer life. Encouragingly, it is a treatment option now endorsed by the National Institutes of Health. Read the NIH report and see the clinical support for weight-loss surgery.

If you'd like to read more about obesity-related health problems, you can click on the links below:

• The Epidemic
• Healthy Living
• Medical Co-Morbidities & Associated Problems

Most health care providers agree that men with more than 25% body fat and women with more than 30% body fat are obese. However, measuring the exact amount of a person's body fat is not easy. The most accurate methods of determining body fat percentage are to weigh a person underwater or to use a specialized type of X-ray test. These methods aren't particularly practical, though, and can only be carried out in specialized facilities.

Because of the impracticalities of these methods, BMI has become the medical standard used to determine whether a person is overweight or obese.

To determine your BMI, use our calculator here!