Basix Wellness

An interactive website to help with diet, nutrition, fitness, and wellness support.

An interactive website to help with diet, nutrition, fitness, and wellness support.

An interactive website to help with diet, nutrition, fitness, and wellness support.

Body Mass Index

Calculators and Tools
Body Mass Index One quick number to assess body composition.
Daily Energy Needs How much energy do you need each day?
Energy Required for Different Activities Want to burn some energy?
Yearly Gain / Loss Estimator Little changes add up over 365 days.
Target Heart Rate Make your exercise more efficient.

To calculate your Body Mass Index, please enter your weight and height in the boxes below and then press the calculate button.

Calculate Body Mass Index

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Result (Body Mass Index):

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The following table shows how to interpret your BMI score:

CLASSIFICATION BMI SCORE
Underweight Less than 18.50
Normal range 18.50 - 24.99
Overweight Equal to or more than 25.00
Obese Equal to or more than 30.00

Body Mass Index and the Importance of Body Composition

Every body is unique and individual. Hardly anyone is built like a fitness model. We need to appreciate our body at any size. We can and should feel good about ourselves, but also remember that there is a link between increased body fat and an increased risk of health problems.

The body is composed of bone, tissues, fluids, and fat. Body composition is the relationship between all the lean tissue and fat in the body. The amount of body fat is important. A high percentage of body fat increases the risk of heart disease, diabetes, high blood pressure, and cancer. Good overall health is linked to a good percentage of fat free mass.

The body mass index (BMI) was created to quickly assess a person's body composition. The BMI is a ratio of weight to height. This chart shows how BMI ranges are determined by height and weight.

Body Mass Index Graph

The Center for Disease Control and Prevention has created a special BMI assessment system for children and teens, aged 2 through 19 years old. The CDC calculator takes into account age and sex differences in body composition occurring during childhood and adolescence. To assess BMI for children and adolescents, use this link to the CDC.

http://apps.nccd.cdc.gov/dnpabmi/Calculator.aspx

The BMI formula has limitations. For example, people who are lean and muscular are frequently classified as overweight. These individuals have a high muscle mass for their height and will have a high BMI.

Learn More - Body Mass Index and Body Composition

The obesity epidemic in the United States is escalating at alarming rates. In 2005, only four states had obesity prevalence rates less than 20%, while 17 states had prevalence rates equal to or greater than 25% (1). Greater obesity rates mean higher rates of lifestyle illnesses such as hypertension, metabolic disorder, diabetes, and cardiovascular disease. Obesity and the other chronic diseases are associated with or caused by a combination of social, cultural, environmental, and behavioral factors (2). The most effective treatment for obesity is behavior modification, integrating balanced nutrition and regular physical activity into one's lifestyle.

What is obesity and how is it defined? The term "overweight" refers to a body weight that is greater than a certain standard, such as the average body weight for a set height. Simple categorizations of "average" or "ideal" body weight based on height-weight tables do not give a clear picture of body composition. Body composition means the relationship between all the lean tissue and fat in the body. The amount of body fat is important. A high percentage of body fat increases the risk of heart disease, diabetes, high blood pressure, and cancer. While health is linked to a good percentage of fat free mass.

The body mass index (BMI) is a quick way to assess body composition. The BMI was created by the World Health Organization as an international standard for classifying body weight. The BMI is widely used in international health promotion research to compare adult obesity rates and to assess the degree of change and the efficacy of obesity intervention programs.

The BMI is a ratio of body mass (weight) to stature (height). BMI is calculated using the following equations. You can use our BMI calculator to find your BMI. This example is for a 6 foot tall (72 inches or 1.8 meters) man weighing 200 lbs (91 kg):

Metric BMI formula = weight (kg)height (m) 2
Example: 91 / (1.8 x 1.8) = 91 /3.24 = 28

English BMI formula = 703.1 x weight (lb)height (in) 2Example: BMI = (703.1 x 200) / (72 x 72) = 140620 / 5184 = 27.1

In the 1988 Surgeon General's Report on Nutrition and Health, there were only four BMI classifications: underweight, normal, overweight, and obese. Currently, there are sub-classifications for the four BMI main classifications to reflect demographics. As shown in the table below, obesity is defined as a BMI of greater than or equal to 30.


CLASSIFICATION BMI
Underweight Less than 18.50
Severe thinness Less than 16.00
Moderate thinness 16.00 - 16.99
Mild thinness 17.00 - 18.49
Normal range 18.50 - 24.99
Overweight Equal to or more than 25.00
Pre-obese 25.00 - 29.99
Obese Equal to or more than 30.00
Obese class I 30.00 - 34.99
Obese class II 35.00 - 39.99
Obese class III Equal to or more than 40.00


It is important to note that the BMI has limitations. The BMI does not take into account that body weight is affected not only by body fat, but also by the increases in bone density, muscle mass, and plasma volume due to regular exercise training. These increases will result in a higher body weight, but does not mean that the individual has more body fat. Misclassification of someone being overweight or obese is also common in lean individuals. These individuals have high amounts of muscle mass in comparison to their height and will have a high BMI.

Although the BMI is frequently used by physicians to determine whether or not an individual has a healthy body weight, there are better ways to assess body composition. These include hydrodensitometry (underwater weighing), dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA), and skinfold measurement.

Hydrodensitometry is based on the Archimedes' principle, that is, an object placed in water has a buoyant force equal to the water it displaces. The most common method of hydrodensitometry is to measure the change in underwater body weight and compare that to dry body weight. Limitations include cost, time and participants must tolerate staying submerging under water while completely exhaling. Hydrodensitometry is the standard by which other body composition methods are validated.

DXA measures bone mineral content. The subject lies above a radionucleotide source of two different x-ray energies. The body is scanned for absorption differences in bone and soft tissue. Soft tissue measurements include fat and lean body mass, which allow for an accurate body composition analysis. A limitation with DXA is its high cost and the time it takes to complete an assessment.

With bioelectrical impedance analysis (BIA), a low level electrical current is sent through the body. Impedence or opposition to the current flow is measured with a BIA analyzer. Total body water is estimated from impedence. Fat-free mass is more conductive than fat. BIA is fast, noninvasive, and nonintrusive. Its accuracy is affected by the quality of instrument used, subject factors (i.e., hydration status, exercise state, menstrual cycle), and the equation used. It tends to over predict the number of lean individuals in a given group.

Skinfold measurements uses calipers to assesses subcutaneous fat at specific sites on the body. Equations are applied to the caliper data to estimate body fat percentage. Skinfold measurement is fast, non-invasive, and easily transportable. Sources of error include technician skill, the quality of the caliper, subject skin preparation and the prediction equation selected.

When performed optimally, hydrodensitometry (underwater weighing), dual-energy X-ray absorptiometry (DXA), bioelectrical impedance analysis (BIA), and skinfold measurement have similar results. All these body composition methods are indirect methods - there is no direct means of assessing body composition in a live human being! However, even though these methods are indirect, the body composition they measure are valuable for tracking change.

Links for more information:

· How to calculate BMI: http://www.nlm.nih.gov/medlineplus/ency/article/007196.htm

· Body composition is often considered a component of fitness: http://www.fitness.gov/fitness.htm

References:

1. Centers for Disease Control and Prevention (CDC). Behavioral Risk Factor Surveillance System Survey Data. Atlanta, Georgia: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 2005.

2. McQueen, DV. Continuing efforts in global chronic disease prevention. Preventing Chronic Disease, 2007;4(2). http://www.cdc.gov/pcd/issues/2007/apr/07_0024.htm

3. U.S. Department of Health and Human Services, 1988.

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