Techniques for Measuring Fat

Various ways of classifying fat, as well as the techniques of the skinfold test and waist-to-hip ratio, were discussed earlier. The following material explains in detail a number of techniques for fat measurement, and illustrates their use via several case studies. A direct measurement of total body fat can only be made by analyzing cadavers (dead people). The amount of fat was correlated with the cadaver s height, width, underwater weight, and skin surface area. These results have resulted in the creation of several techniques for indirectly assessing body fat in 

Please calculate the BMI of a 60-kg female who is 1.60 meters tall. Please calculate your own BMI. 

The BMI can be calculated using a scale, ruler, and pocket calculator. BMI values of 20-25 kg/are associated with the least health risk. A BMI of 30 kg/m is associated with serious risk for premature death due to obesity. BMI values xmder 16 kg/m suggest an eating disorder such as anorexia nervosa or bulimia. 

Example of Use of Body Mass Index in a Study of Diabetics 

Let us dwell on the topic of obesity and weight loss for a bit longer. The American Diabetes Association has recommended that adults with NIDDM exercise for at least 20 min/day at 50% of the maximal O2 consumption rate (Ruderman and Schneider, 1992). This recommendation was designed to promote weight loss, since about 85% of people with NIDDM are also obese. However, evidence also suggests that exercise alone, even without weight loss, can improve the body s sensitivity to insulin. 

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The last main section, functional properties, comprises descriptions of techniques for measuring ingredient properties and end use properties of milk fat and milk fat-based products. 

Dilatometry is a technique for measuring the solid fat index (SFI), which is an estimate of the mass fraction of a fat that is solid at the temperature of measurement. 

DSC is a particularly useful technique for measuring temperature and heat of transition, two properties of considerable importance with respect to the thermal behavior of fats. 

This chapter will review the relative contributions of exercise and food intake to changes in body weight and more specifically body composition. The emphasis of this chapter is on exercise as a modality for fat reduction and fat-free weight maintenance with the focus on aerobic exercise which has greater potential to modify body composition due to larger effects on energy balance. The first section reviews the effects of aerobic exercise on body composition in humans. The second section addresses techniques for measurement of body composition and limitations of these measurements in humans. The third section examines the use of experimental animals for studies of exercise and body composition, and the fourth section examines the interactions of diet and exercise. 

Several techniques have been devised for measuring fat and its distribution in living humans. Terms used to refer to fat s distribution include subcutaneous fat, visceral fat, android (male type) obesity, and gynoid (female type) obesity. The science of measurement of body size, weight, and proportions is called anthropometry. Hence, the following techniques are methods of anthropometry. 

The most commonly used methods for measuring chlordecone and its degradation products in air, water, soil, sediment, fish, shellfish, and animal fat are similar to those used for mirex (i.e., GC/ECD techniques and confirmation by GC/MS). Because of the polar nature of chlordecone, the removal of... 

Infant formula, tocopherol/tocotrienol analysis, 479, 487, 489 (table) Infrared spectroscopy, see also Fourier transform infrared spectroscopy fat measurement, 572 trans fatty acids, 505 Infrared/ultrasonic scanner for emulsion creaming, 597-598 Injection techniques for GC, 449 Insoluble recombinant proteins, purification of, 276... 

Many of the tests described involve physical properties such as refractive index, viscosity or melting point of the fat, of the fatty acids or of the lead salts of the fatty acids. However, there were also many chemical tests such as Reichert, Polenske, iodine, saponification and acetyl values. These all gave information as to the composition of the fat, some information as to fatty acid composition, others as to other non-glyceride components of the fat. Thus the iodine value is a measure of unsaturated fatty acids in the fat, now obtainable in more detail from a fatty acid profile. Similarly the Reichert value is a measure of volatile fatty acids soluble in water. For most purposes this means butyric acid, and so the modem equivalent is the determination of butyric acid in the oil. The modem method for milk-fat analysis is thus carrying out the analysis in a similar way to the Reichert determination, but uses a technique that is less dependent on the exact conditions of the analysis and is thus less likely to be subject to operator error. The Reichert value could be useful, in theory, even if milk fat was not present. Lewkowitsch notes that some other oils do give high values. Porpoise jaw oil has a value almost twice that of milk fat, while some other oils also have significant values. It is unlikely that one would have come across much porpoise jaw oil even in 1904, and even less likely today. 

It should be mentioned that DSC and NMR do not measure the same parameters, and in this way, these techniques are complementary. DSC is a dynamic method, which gives information about the transitions between different phases of lipids, whereas NMR allows quantitation of liquid and solid phases at equilibrium. Indeed, NMR and DSC methods give different values for the solid fat index (SFI) (Walker and Bosin, 1971 Norris and Taylor, 1977) NMR values are much lower than those given by DSC below 20°C. For example, for milk fat at 5°C, DSC and NMR indicate 78.1% and 43.7% solid fat, respectively. The observed difference can be explained by the presence of an amorphous phase which, due to its melting enthalpy, is seen as a solid by the DSC method. Using time-domain NMR, Le Botlan et al. (1999) showed that in milk fat samples, an intermediate component exists between the solid and liquid phases, constituting about 6% of an aged milk fat. 

This measurement is claimed to be more reproducible than the slip point (see below), and is the most widely accepted technique for determining melting point (Rossell, 1986 Kaylegian and Lindsay, 1994). It is the method usually used for milk fat. 

As pointed out earlier in this review, increasing the level of dietary calcium decreases the zinc bioavailability from phytate-containing foods. Presumably the mechanism is through the formation of chemical complexes containing zinc, phytate and calcium which are insoluble at intestinal pH and nonabsorbable (24). Recently, our laboratories used slope ratio techniques to compare the bioavailability of zinc contained in calcium sulfate-and in magnesium chloride-precipitated soybean curd (Tofu) to that of zinc added as the carbonate to egg white diets by slope ratio techniques (25). Total dietary calcium level in all diets was adjusted to 0.7% with calcium carbonate. The results (not shown) indicated that the relative availability of zinc from both tofu preparations was 51% as measured by weight gain and 36-39% for bone zinc. These results are similar to those reported for full fat soy flour (16) in Table I. 

A useful measure of an individual s physical condition is the fraction of his or her body that consists of fat. This problem describes a simple technique for estimating this fraction by weighing the individual twice, once in air and once submerged in water. 

Flavor Components of Fats and Oils, Lipid Oxidation Measurement Methods, Marine Mammal Oils, Modification of Fats and Oils via Chemical and Enzymatic Methods, Novel Separation Techniques for Isolation and Purification of Fatty Acids and Oil By-Products, Quality Assurance of Fats and Oils, Tree Nut Oils. 

Analytical methods for measuring hydroperoxides in fats and oils can be classified as those determining the total amount of hydroperoxides and those based on chromatographic techniques giving detailed information on the structure and the amount of specific hydroperoxides present in a certain oil sample (8). The PV represents the total hydroperoxide content and is one of the most common quality indicators of fats and oils during production and storage (9, 18). A number of methods have been developed for determination of PV, among which the iodometric titration, ferric ion complex measurement spectrophotometry, and infrared spectroscopy are most frequently used (19). 

Skinfoid measurements reflect the thickness of layers of fat at specific points of the body. In contrast, the technique of densitometry is sensitive to the proportion of fat in the entire body. Density, whether measured by chemists, physicists, or dieticians always means mass/volume grams/ml). The density of a human being is often measured by using underwater weighing- This technique requires a tub of water, a scale for measuring the subject s weight, and a special chair that is attached to the scale. The subject needs to have defecated and urinated shortly... 

Classification of Fat Diseases Associated with Obesity Early Studies of Obesity in Rodents Short-Term and Long-Term Controls of Body Weight Human Psychology of Obesity Summary of Techniques Used for Measuring Adipose Tissue Types of Fat... 

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