Diagnostic Tests for Overweight
Diagnostic Test list for Overweight: The list of diagnostic tests mentioned in various sources as used in the diagnosis of Overweight includes:
- Body Mass Index (BMI) - BMC 25..<30 is overweight; BMI >= 30 is obesity
- Weight-for-height charts
- Skinfold thickness measurement
- Bioelectrical impedance analysis (BIA)
Tests and diagnosis discussion for Overweight: Body mass index (BMI) is a measure of body weight relative to height. You can use BMI to see whether you are underweight, normal weight, overweight, or obese. Use the body mass index table below to find your BMI.
- Find your height in the left-hand column.
- Move across in the same row to the number closest to your weight.
- The number at the top of that column is your BMI. Check the word above your BMI to see whether you are normal weight, overweight, or obese.
Body Mass Index Table
|Body Weight (pounds)|
|Body Weight (pounds)|
Source: Adapted from Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report.1
If you think that your child is overweight, it is important to talk with your child's doctor. A doctor is the best person to determine whether your child has a weight problem. Physicians will measure your child's weight and height to determine if your child's weight is within a healthy range. A physician will also consider your child's age and growth patterns to determine whether your child is overweight. Assessing overweight in children is difficult because children grow in unpredictable spurts.
For example, it is normal for boys to have a growth spurt in weight and catch up in height later. It is best to let your child's doctor determine whether your child will "grow into" a normal weight. If your doctor finds that your child is overweight, he or she may ask you to make some changes in your family's eating and activity habits. 2
A number of methods are used to determine if an individual is overweight or obese. Some of them are based on mathematical calculations of the relation between height and weight--others are based on measurements of body fat. These methods are described below.
Body Mass Index
Body Mass Index (BMI) can be used to measure both overweight and obesity in adults. It is the measurement of choice for many obesity researchers and other health professionals. BMI is a direct calculation based on height and weight, and it is not gender-specific. Most health organizations and published information on overweight and its associated risk factors use BMI to measure and define overweight and obesity. BMI does not directly measure percent of body fat, but it provides a more accurate measure of overweight and obesity than relying on weight alone.
BMI is found by dividing a person's weight in kilograms by height in meters squared. The mathematical formula is:
weight (kg)/height squared (m2).
To determine BMI using pounds and inches, multiply your weight in pounds by 704.5,* then divide the result by your height in inches, and divide that result by your height in inches a second time3
The National Institutes of Health (NIH) identify overweight as a BMI of 25-29.9 kg/m2, and obesity as a BMI of 30 kg/m2 or greater. However, overweight and obesity are not mutually exclusive, since obese persons are also overweight.1 Defining overweight as a BMI of 25 or greater is consistent with the recommendations of the World Health Organization 2 and most other countries. 3
Weight-for-height charts are another measure used to determine if a person is overweight (although they do not measure body fat). These charts, which have been used by doctors and other health care workers for decades, usually give a range of acceptable weights for a person of a given height. Many versions of weight-for-height charts exist, some showing different acceptable weight ranges for men and women. Health care workers often disagree over which is the best chart to use. The 2000 Dietary Guidelines for Americans, published jointly by the U.S. Departments of Agriculture and Health and Human Services, provide the most up-to-date weight-for-height chart. The healthy weight range in this chart corresponds to a BMI between 18.5 and 25. 3
Measurements of Body Fat
There are a number of ways to measure body fat. Historically, the standard method is to weigh a person underwater; this procedure is limited to laboratories with specialized equipment.
Other simpler methods for measuring body fat include skinfold thickness measurements and bioelectrical impedance analysis (BIA). Skinfold thicknesses are measures of the subcutaneous (lying just beneath the skin) fat at specific sites of a person's body, such as the triceps (the back of the upper arm). Accurate measurements of skinfold thickness depend on the skill of the examiner and may vary widely when measured by different examiners.
To measure body fat using BIA, a harmless amount of an electrical current is sent through the body. The body's ability to conduct an electrical current reflects the total amount of water in the body. Generally, a higher percent body water indicates a larger amount of muscle and lean tissue. Mathematical equations are used to translate the percent body water measure into an indirect estimate of body fat and lean body mass. A standard method should be used to measure bioelectrical impedance because dehydration, recent exercise, skin and room temperature, and placement of electrodes all can affect test results. To obtain the most precise reading, the person being tested should fast for at least 4 hours and lie down for at least several minutes prior to testing. BIA may not be accurate in severely obese individuals, and it is not useful for tracking short-term changes in body fat brought about by diet or exercise.
In addition to body weight and height measurements, health professionals may also rely on a person's waist measurement to determine the location of excess body fat and the corresponding health risks. Analogous to BMI, health risks increase as waist circumference increases. A woman whose waist measures more than 35 inches and a man whose waist measures more than 40 inches may be at particular risk for developing health problems. Studies indicate that increased abdominal or upper body fat is related to the risk of developing heart disease, diabetes, high blood pressure, gallbladder disease, stroke, and certain cancers, and is associated with overall mortality (likelihood of death). Body fat concentrated in the lower body (around the hips, for example) may be less harmful in terms of mortality and morbidity (likelihood of disease), with the exception of varicose veins and orthopedic problems3
The definitions or measurement characteristics for overweight and obesity have varied over time, from study to study, and from one part of the world to another. The varied definitions affect the prevalence statistics of studies and make it difficult to compare data from different studies and from different countries.3
The words obesity and overweight are generally used interchangeably. However, according to the Institute of Medicine report, their technical meanings are not identical. Overweight refers to an excess of body weight that includes all tissues, such as fat, bone and muscle. Obesity refers specifically to an excess of body fat. It is possible to be overweight without being obese, as in the case of a body builder who has a substantial amount of muscle mass. It is possible to be obese without being overweight, as in the case of a very sedentary person who is within the desirable weight range but who nevertheless has an excess of body fat. However, most overweight people are also obese and vice versa. Men with more than 25 percent and women with more than 30 percent body fat are considered obese. The USFDA has released a chart detailing recommended weights relative to height; women should be in the lower end of their appropriate weight range, according to the chart.4
Diagnosis of Overweight: medical news summaries: The following medical news items are relevant to diagnosis of Overweight:
- About metabolic syndrome
- Different types of sleep disorders plague many millions of Americans
- Overweight men risk having their prostate cancer misdiagnosed
1. excerpt from Am I at Risk for Type 2 Diabetes: NIDDK
2. excerpt from Helping Your Overweight Child: NIDDK
3. excerpt from NIDDK _ Statistics Related to Overweight and Obesity: NIDDK
4. excerpt from Diet: NWHIC
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