Diagnostic Tests for Obesity

Diagnostic Test list for Obesity:

The list of diagnostic tests mentioned in various sources as used in the diagnosis of Obesity includes:

• Physical examination
  • Calculate the Body mass index (BMI) = weight (kg) / height (m2)
  • Obesity is defined as a BMI of 30-40. Morbid obesity is defined as a BMI of over 40
  • Calculate Waist-Hip ratio. Obese people with a high waist-hip ratio (over 1.0 in men and over 0.9 in women) have a significantly greater risk of diabetes mellitus, stroke, heart attacks and early death than equally obese people with lower waist-hip ratio
  • Determine the distribution of body fat. If the obesity is predominantly abdominal, especially with a moon-shaped face, must consider Cushing's syndrome. Type 2 diabetes is also associated with abdominal obesity. If the obesity is predominantly of the lower legs, must consider lipodystrophy
  • Measure Blood pressure. Obesity will increase blood pressure directly. Cushing's syndrome is associated with high blood pressure
  • Examine for signs of Cushing's syndrome - e.g. thin skin, bruising, high blood pressure, stretch marks, proximal muscle weakness, acne, pigmentation, excess hair on face, frontal balding in males, moon face, buffalo hump, truncal obesity, fluid retention.
  • Examine for signs of hypothyroidism - e.g. slow heart rate, slowedreflexes, coarse dry brittle hair, dry cool skin, goiter.
  • Examine for signs of Acromegaly such as excessive size of hands, feet, nose, lips, face, jaw and tongue
  • Examine for signs of atherosclerosis (hardening of the arteries) including reduced or absent peripheral pulses, enlarged heart and bruits heard in the carotid arteries in the neck. Obesity is a major risk factor for atherosclerosis which in turn increases the risk of heart attacks, strokes, kidney failure and peripheral vascular disease
• Blood tests
  • Full blood count
  • Electrolytes - looking for low potassium in Cushing's syndrome due to adrenal tumors.
  • Renal function tests
  • Liver function tests
  • Thyroid function test
  • Fasting blood sugar level. Diagnosis of Diabetes mellitus requires fasting blood sugar level to be greater or equal to 7.0 mmol/L
  • Fasting blood lipids, including total cholesterol, LDL, HDL, triglycerides
  • 24-36 hour fasting blood sugar and insulin levels, if suspect insulinoma
  • 5 hour glucose tolerance test, if suspect insulinoma
  • Serum cortisol level, if suspect Cushing's syndrome
  • Cortisol suppression test, if suspect Cushing's syndrome
  • Testosterone
  • Chromosomal analysis will help diagnose Klinefelter's syndrome (in males), Turner's syndrome (in females) and Prader-Willi syndrome in children
• Urine tests
  • Urine analysis to test for sugar
  • 24 hour free cortisol, if suspect Cushing's syndrome
• Radiological investigations
  • Chest X-Ray may detect signs of heart disease due to obesity
  • Adrenal gland CT scan may detect adrenal tumors that may cause 15% of cases of Cushing's syndrome
  • Pituitary gland CT scan or MRI - may detect pituitary tumor that may cause 60% of cases of Cushing's syndrome.
  • Chest X-Ray and/or CT scan may detect a lung cancer that rarely may produce ACTH hormone that can cause Cushing's syndrome
  • Pelvic ultrasound scan will help diagnose polycystic ovaries
• Electroencehalogram (ECG) - to screen for heart disease due to obesity.
• Body Mass Index (BMI) - BMC 25..<30 is overweight; BMI >= 30 is obesity.
• Weight-for-height charts
• Skinfold thickness measurement
• Bioelectrical impedance analysis (BIA)

Home Diagnostic Testing

These home medical tests may be relevant to Obesity causes:

• Diet & Weight Loss: Home Testing:
  • Home Weight Testing
  • Home Body Fat Testing (BMI)
  • Home Body Fat Monitoring
  • Home Fitness Testing
• Diabetes: Related Home Testing:
  • Home Diabetes Testing
  • Home Blood Glucose Test Kits
  • Home Urine Glucose Tests
  • Home Urine Ketone Tests
  • Home Diabetes HbA1c Tests
  • Home Microalbumin Tests (Kidney)
  • Home Urine Protein Tests (Kidney)
  • Home Kidney Health Tests
  • Home Eye Health Tests

Tests and diagnosis discussion for Obesity:

Everyone needs a certain amount of body fat for stored energy, heat insulation, shock absorption, and other functions. As a rule, women have more body fat than men. Most health care providers agree that men with more than 25 percent body fat and women with more than 30 percent body fat are obese.

Measuring the exact amount of a person's body fat is not easy. The most accurate measures are to weigh a person underwater or to use an X-ray test called Dual Energy X-ray Absorptiometry (DEXA). These methods are not practical for the average person, and are done only in research centers with special equipment.

There are simpler methods to estimate body fat. One is to measure the thickness of the layer of fat just under the skin in several parts of the body. Another involves sending a harmless amount of electricity through a person's body. Both methods are used at health clubs and commercial weight loss programs. Results from these methods, however, can be inaccurate if done by an inexperienced person or on someone with severe obesity.

Because measuring a person's body fat is difficult, health care providers often rely on other means to diagnose obesity. Weight-for-height tables, which have been used for decades, usually have a range of acceptable weights for a person of a given height. One problem with these tables is that there are many versions, all with different weight ranges. Another problem is that they do not distinguish between excess fat and muscle. A very muscular person may appear obese, according to the tables, when he or she is not.

In recent years, body mass index (BMI) has become the medical standard used to measure overweight and obesity. (Source: excerpt from Understanding Adult Obesity: NIDDK)

Although the BMI ranges shown in the table are not exact ranges of healthy and unhealthy weight, they are useful guidelines. A BMI of 25 to 29.9 indicates a person is overweight. A person with a BMI of 30 or higher is considered obese. (Source: excerpt from Understanding Adult Obesity: NIDDK)

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.

Source: Adapted from Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report. (Source: excerpt from Am I at Risk for Type 2 Diabetes: NIDDK)

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 time (Source: excerpt from NIDDK _ Statistics Related to Overweight and Obesity: NIDDK)

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. (Source: excerpt from NIDDK _ Statistics Related to Overweight and Obesity: NIDDK)

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. (Source: excerpt from NIDDK _ Statistics Related to Overweight and Obesity: NIDDK)

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 problems (Source: excerpt from NIDDK _ Statistics Related to Overweight and Obesity: NIDDK)

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. (Source: excerpt from NIDDK _ Statistics Related to Overweight and Obesity: NIDDK)

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. (Source: excerpt from Diet: NWHIC)

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