Magnetic-resonance imaging used for determining fat distribution in obesity and diabetes

Article Abstract:

It has been known for some time that obesity is a serious health risk. In recent years, it has also become clear that the distribution of fat on the body is important in determining the health risk. For example, studies have reported that excessive abdominal fat is more likely to increase the risk of developing diabetes, high blood pressure and heart disease. The relative risk is determined by measuring the waist-to-hip ratio (the distance around the abdomen divided by the distance around the hips). The larger the ratio, the greater the amount of abdominal fat compared with hip fat, and the greater the health risk. Several studies have used an imaging technique called computed tomography (CT scan) to determine the distribution of body fat in obese individuals. Magnetic resonance imaging (MRI) also can be used for this purpose, and it offers the advantage that it does not use ionizing radiation. Rather, during MRI the subject is exposed to a strong magnetic field followed by a radio frequency. This article describes the results of a study designed to evaluate body fat distribution using MRI in 24 obese women with non-insulin-dependent diabetes (NIDDM) and in 12 obese but nondiabetic women. The women with NIDDM had significantly greater amounts of abdominal fat than those without NIDDM, but the amount of subcutaneous fat (beneath the skin layer) was the same in both groups. To determine how weight loss affects body fat distribution, 10 of the subjects without NIDDM were placed on a low-calorie diet. The women lost an average of 23 pounds, along with 13 percent of their subcutaneous fat and 28 percent of their abdominal fat. These findings indicate that weight loss can reduce the amounts of both abdominal and subcutaneous fat. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Evaluation, Diabetics, Overweight persons, Magnetic resonance imaging

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Effect of obesity on bioelectrical impedance

Article Abstract:

Estimating the composition of the body mass from indirect and simple measurements techniques can be useful when current procedures would be inconvenient, stressful or made impossible by the patient's other needs. For instance, measurement of the body's lean mass is achieved by submerging and weighing individuals in water, a technique that is beyond the scope of most clinical environments. Recent equipment has become available to estimate lean body mass and fat content of individuals by a bioelectrical impedance method that is fast, inexpensive and convenient for office practice. The purpose of this study is to correlate measurements taken with the indirect bioelectrical impedance devices with those take by the standard techniques. A total of 87 healthy adults of various degrees of obesity served as subjects. Most were members of a weight-loss program, but normal-weight hospital employees were recruited as voluntary subjects. The group was composed of 25 male and 62 females with ages from 17 to 74 years. Their body mass ranged from 19.6 to 53.3 percent and body fat varied from 8.8 to 59 percent. The patients weight and height were recorded and the percentage of body fat was calculated by comparing the air weight to the weight of the body under water. The bioelectric method provided values that correlated well with direct measurements up to a body fat value of 42 percent. At this value and higher the bioelectric method tended to overestimate the free-fat (lean body) mass. The data suggest that the bioelectrical impedance method is an accurate and convenient method of obtain body composition data as long as care is taken in assessing the data of greatly obese persons.

Impedance, Bioelectric, Bioelectric impedance

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Skinfold thickness measurements in obese subjects

Article Abstract:

Skinfold thicknesses are used to estimate the percent body fat of an individual and to diagnose obesity. To measure a skinfold a clinician pinches a fold of skin and underlying fat tissue between two fingers and then applies calipers, which pinch and measure the skinfold. Some have suggested that 'fatfold' is a better term because it is the subcutaneous fat that is really being measured, not the skin. Skinfolds are measures at various body sites, such as the arm, abdomen, upper back and thigh. The various measurements for an individual are put into an equation, which estimates the percent body fat. However, the accuracy of the skinfold method has been questioned and other methods of evaluating body composition have been developed. This study assessed the accuracy of skinfold thicknesses by comparing this method with three other approaches for body composition analysis; these methods were bioelectrical impedance, underwater weighing, and total body water by deuterium dilution. The 105 subjects varied greatly in fatness, ranging from 3 to 61 percent body fat. A comparison of the results obtained using the four methods indicated that skinfolds and underwater weighing were correlated as closely as bioelectrical impedance and underwater weighing. However, in the obese subjects, the skinfold and impedance methods may have underestimated body fat. The difficulty in taking skinfold measurements on obese subjects was that the calipers did not open wide enough to measure skinfolds at all the body sites, and complete calculations could not be performed. (Consumer Summary produced by Reliance Medical Information, Inc.)

Analysis, Diagnosis, Skinfold thickness

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