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Body Mass Index Information

You can download Body Mass Index Calculator (it has more features) or use our Online BMI Calculator

Also, you can visit our Nutrition Database to see nutrition information and facts about many products.

The body mass index (BMI) is a calculated number used to determine healthy weight ranges for humans. It was developed by the Belgian polymath Adolphe Quetelet in the course of working out his system of 'social physics', between 1830 and 1850 (and is therefore also known as the Quetelet Index). It has been used to define the medical standard for obesity measurement in several countries since the early 1980s, and is the main measure employed in World Health Organization obesity statistics. It is equal to the weight in kilograms, divided by the square of the height in metres:

Body Mass Index

(In U.S. customary units, it is 703.07 times the weight in pounds, divided by the square of the height in inches.)

The exact index values used to determine weight categories vary from authority to authority, but in general a BMI less than 18.5 is underweight and may indicate malnutrition, an eating disorder, or other health problem, while a BMI greater than 25 is overweight and above 30 is considered obese. These range boundaries apply to adults over 20 years of age.

Since BMI does not take into account a person's body fat percentage, it is possible to have an above average body weight and BMI, but not be obese. A bodybuilder, for example, can have a BMI above 30 because of a high percentage of muscle mass. If they also had a low percentage of body fat, they would not need to lose weight to be healthy.

The U.S. National Health and Nutrition Examination Survey of 1994 indicates that 59% of American men and 49% of women have BMIs over 25. Extreme obesity — a BMI of 40 or more — was found in 2% of the men and 4% of the women.

Body mass index calculations are not just for adults though, and they can be used to identify the growing number of overweight children. BMI for kids aged 2 to 20 years is calculated just like it is for adults, but it is interpreted differently. Instead of set cutoff numbers for being underweight and overweight, like for adults, it is their BMI percentile that is important.

For children, a BMI that is less than the 5th percentile is considered underweight and above the 95th percentile is overweight. And children with a BMI between the 85th and 95th percentile are considered to be at risk of becoming overweight.


Recommended BMI Thresholds

Underweight - 20
Ideal - 20-24.9
Overweight - 25-29.9
Obese - 30 or more
Extremely obese - 40 or more



Note: These recommended distinctions along the linear scale may vary from time to time and country to country, making global, longitudinal surveys problematic. In 1998, the US NIH brought US definitions into line with WHO guidelines, lowering the normal/overweight cut-off from BMI 27 to BMI 25. This had the effect of redefining approximately 30 million Americans, previously 'technically healthy' to 'technically overweight'. The WHO uses the term 'pre-obese' where the USA uses 'overweight'. It also recommends lowering the normal/overweight threshold for South East Asian body types to around BMI 23, and expects further revisions to emerge from clinical studies of different body types.

 

Weight Losss

In the context of physical health, weight loss is the process of losing body weight, usually by losing fat. To achieve healthy weight loss, most experts recommend a combination of healthy eating patterns and regular physical exercise. Some people try to lose weight by using drugs such as fenfluoramine, nicotine or cocaine (see Anti-obesity drugs), herbs such as ephedra, or surgery such as liposuction. A loss of weight can also be the symptom of some mental or physical diseases or disorders, such as anorexia nervosa or the cachexia associated with cancer or AIDS.

Dieting

Dieting is the practice or habit of eating (and drinking) in a regulated fashion, usually with the aim of losing weight. It is also used in some cases to gain weight or to regulate the amounts of certain nutrients entering the body.

Most typically, "dieting" means eating in a carefully planned way in an attempt to reduce excess body fat and decrease bodily measurements, such as clothing size.

There exist a (sometimes confusing) multitude of weight loss techniques, many of which are ineffective. What works for one person will not necessarily work for another, due to metabolic differences and lifestyle factors.

Successful weight loss diet is all about energy in versus energy out. If a person takes in less food energy than he or she expends over a period of time, the person may burn fat and subsequently lose weight.

Diets affect the energy in component of the energy balance by limiting or altering the distribution of foods. Techniques that affect the appetite can limit energy intake by affecting the desire to overeat. This can be attempted by focusing on foods that are filling, through the use of certain appetite-suppressing drugs, or through activities such as mild exercise, that affect appetite. Other techniques address habitual or emotional eating.

Affecting the energy out component is the focus of fitness and exercise programs. These might also be included in a comprehensive "diet."

Dieting in order to lose weight does just that -- you lose weight, water, some fat and muscles. Since muscles are denser, you lose a lot of weight, but little in size. Fat is bulkier, so a three pound fat loss can cause a size loss.

To lose a pound of fat, one must create a caloric deficit of approximately 3,500 calories (37,600 kJ per kilogram of fat); therefore, if a person creates a deficit of 500 calories per day, the person will lose approximately 1 pound of fat per week (5,400 kJ per day to lose a kilogram a week).

Muscle-loss during weight-loss can be restricted by regularly lifting weights and by a high protein intake. (It is said that 0.8 to 1.0 g of protein per pound of body weight (1.76 to 2.20 g/kg) per day is sufficient.)