Upper body fat

Individuals with more upper body fat (left) have greater health risks than pear-shaped individuals (right). 

Adipose Tissue Androgens promote truncal-abdominal fat deposition and favor development of upper body obesity. In contrast to gluteofemoral (lower body) fat, upper body fat accumulation, particularly visceral fat, is characterized by an increase in fat cell size, increased lipoprotein lipase (LPL) activity, enhanced lipolysis, and reduced response to the antilipolytic effect of insulin. This explains why androgen-dominated states favor insulin resistance. 

Upper body fat deposition tends to occur more by hypertrophy of the existing cells, whereas lower body fat deposition is by differentiation of new fat cells (hyperplasia). This may partly explain why many women with lower body obesity have difficulty losing weight. 

The mechanisms whereby body fat distribution may be associated with diabetes independently of overall adiposity are still unresolved but the subject of intense research attention. Subjects with predominantly upper-body fat distribution are more insulin-resistant than subjects equally obese but with a fat distribution predominantly in the lower body. Upper body obesity is associated primarily with fat cell hypertrophy (increased adipocyte size) while lower body fat distribution is associated more with fat cell hyperplasia (increased number of adipocytes). As fat cells enlarge, they become more resistant to insulin. The adipose tissue, however, accounts for only about 5% of total body glucose disposal, so that insulin resistance in this tissue alone should not account for significant increases in total body insulin... 

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Excess fat can be located in the central abdominal area (android, upper body obesity). This fat is associated with a greater risk for hypertension, insulin resistance, diabetes, dyslipidemia, and coronary heart disease. That distributed in the lower extremities (gynoid, lower body obesity) is relatively benign, healthwise. 

Ultrasound, measuring body fat, 383 Units of energy, 274-276 Unsaturated fatty acids, 320, 746-747 Untranslaled regions (UTKsl, 37 Upper body fai, 385... 

Adipose Tissue Estrogenic states favor subcutaneous fat deposition in the gluteofemoral region (lower body) and promote lower body obesity. Current evidence suggests that a lower body fat pattern, or a low upper-lower body circumference ratio (referred to as gynoid ), is associated with a lower incidence of coronary heart disease and may be due to the effect of estrogen on lipoprotein metabolism. 

It is the male pattern of upper body segment obesity that is associated with the major health risks, and in a number of studies assessment of the pattern of fat distribution by measurement of either the waist—hip ratio or the subscapular skinfold thickness (section 6.1.2.5) shows a greater correlation with the incidence of hypertension, diabetes and coronary heart disease than does BMI alone. 

It has been a consistent finding that Type II diabetes is almost invariably associated with obesity but of more fundamental interest is its association with a particular distribution of body fat. The excessive adipose tissue characteristic of obesity tends to be distributed in the upper body, including the waist (android or upper body obesity) or the lower body, including the hips and buttocks (gynoid or lower body obesity). The former is more characteristic of men and is more closely associated with Type II diabetes, hyperlipidaemia and other metabolic disorders while the latter is more usually seen in women and has fewer adverse metabolic implications. These relationships are so strong that risk can be assessed by a relatively simple index the ratio of waist to hip circumference. 

Since in mammalian species metals first need to be assimilated from dietary sources in the intestinal tract and subsequently transported to the cells of the different organs of the body through the bloodstream, we will restrict ourselves in this section to the transport of metal ions across the enterocytes of the upper part of the small intestine (essentially the duodenum), where essentially all of the uptake of dietary constituents, whether they be metal ions, carbohydrates, fats, amino acids, vitamins, etc., takes place. We will then briefly review the mechanisms by which metal ions are transported across the plasma membrane of mammalian cells and enter the cytoplasm, as we did for bacteria, fungi and plants. The specific molecules involved in extracellular metal ion transport in the circulation will be dealt with in Chapter 8. 

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