Impact of obesity on metabolism in men and women. Importance of regional adipose tissue distribution

Alterations in low-density lipoproteins in subjects with abdominal adiposity

Abdominal adiposity, as indexed by the waist to hip girth ratio (WHR), has been associated with increased risk and incidence of coronary heart disease (CHD). The purpose of this study was to determine if this enhanced risk is related to alterations in the structure of low density lipoproteins (LDL). LDL were isolated from nine nonobese men with an average WHR of 1.046 and nine nonobese men with a WHR of 0.94, who were matched on age (45.6 +/- 2.7 v 47.7 +/- 2.3 mean +/- SEM) percent body fat (26.5 +/- 0.5 v 26.1 +/- 0.9), and body mass index (27.3 +/- 0.6 v 26.3 +/- 0.6). The average molecular weight of LDL from the subjects with a high WHR was lower than that of subjects with low WHR (2.70 v 3.02 x 10(6) d), the average hydrated density higher (1.050 v 1.040 g/mL), and the mobility (Rf) on 2% to 16% polyacrylamide gradient gel electrophoresis higher. Subfractionation by equilibrium density ultracentrifugation showed that the LDL of subjects with a high WHR was predominantly in the heavy density range (1.038 to 1.048 g/mL) compared with the LDL of subjects with low WHR, which was in the lighter density range (1.030 to 1.040 g/mL). Chemical analysis of the subfractions showed that the peak density fractions of LDL of subjects with a high WHR had a lower cholesterol to protein ratio than the peak density fractions of LDL of subjects with low WHR. Electron microscopy of these peak density fractions showed that LDL of subjects with high WHR was smaller than that of subjects with low WHR. These characteristics of LDL of subjects with abdominal adiposity closely resemble the properties of LDL of patients with documented CHD. It is concluded that the increased risk of CHD associated with abdominal adiposity may be due in part to the alterations in LDL characteristics, and that these alterations in LDL are independent of the degree of obesity.

Associations of abdominal adiposity, fasting insulin, sex hormone binding globulin, and estrone with lipids and lipoproteins in post-menopausal women

The associations of abdominal adiposity, fasting serum levels of insulin, and sex hormones with blood lipids, lipoproteins, and apolipoproteins A-I and B were studied cross-sectionally in 75 healthy, postmenopausal white women. In univariate analyses, abdominal adiposity (increased waist-to-hip girth ratio) and fasting insulin concentrations were negatively and significantly associated (P less than 0.05) with plasma high density lipoprotein cholesterol (r = -0.47 and -0.38, respectively) and apolipoprotein A-I (r = -0.37 and -0.36), and positively associated with log triglycerides (r = 0.54 and 0.33) and apolipoprotein B (r = 0.43 and 0.22). Sex hormone binding globulin was positively and significantly associated with high density lipoprotein cholesterol (r = 0.32) and negatively associated with log triglyceride (r = -0.45) and apolipoprotein B (r = -0.36). Estrone was positively and significantly associated with high density lipoprotein cholesterol (r = 0.27), apolipoprotein A-I (r = 0.23) and negatively associated with low density lipoprotein cholesterol (r = -0.24) and apolipoprotein B (r = -0.25). Total estradiol, free estradiol, free testosterone, and total testosterone were more weakly associated with the lipid measures. In multivariate analyses, abdominal adiposity remained significantly associated with high density lipoprotein cholesterol, log triglycerides, apolipoproteins A-I and B after adjustment for sex hormone binding globulin, estrone, and insulin concentrations. Insulin remained associated only with apolipoprotein A-I after adjustment for abdominal adiposity, estrone, and sex hormone binding globulin. Sex hormone binding globulin remained marginally associated with log triglyceride (P = 0.07) after adjustment for the remaining three factors. Estrone remained significantly associated with high density lipoprotein cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)

Obesity, adipose tissue distribution and health in men--the study of men born in 1913

Recent studies suggest that cardiovascular disease is associated with abdominal distribution of adipose tissue rather than obesity in terms of total body fat. A number of other variables, known to be associated with obesity, were therefore examined in a cohort of randomly selected middle-aged men in relation to abdominal distribution of adipose tissue, measured as the ratio of the circumferences of the waist and hips (WHR), as well as to degree of obesity, measured as body mass index (BMI). These variables included anthropometric variables, cardiovascular risk factors as well as socioeconomic factors and physical health. Increased WHR, independent of BMI, was negatively associated with height, and hip circumference. Positive associations were found with blood pressure, cholesterol, triglycerides, fibrinogen and smoking. In addition positive associations were found with low social class and social group, illness in terms of sick leave, frequent use of health facilities such as X-rays, as well as diseases such as peptic ulcer. In sharp contrast to this, BMI, independent of WHR, was not associated with physical health variables or social class. Generalized obesity seemed to be associated with good health in the variables measured. There were positive associations to various anthropometric variables, including lean body mass. High BMI was also associated with elevated blood pressure and triglycerides. Several of the indicators of poor health traditionally associated with obesity thus do not seem to be characteristic for obesity in middle-aged men selected at random from the population but rather for an abdominal fat distribution, independent of obesity.

Correlation of intraabdominal fat accumulation and left ventricular performance in obesity

The correlation of intraabdominal visceral fat accumulation and left ventricular performance was investigated in 37 obese patients who had 154 +/- 23% of ideal body weight. The left ventricle was studied noninvasively by means of echocardiography, whereas the distribution of body fat was determined by computed tomography. The end-diastolic left ventricular dimension and stroke volume were greater in obese patients than in non-obese control subjects. Not only the absolute values of these parameters, but also the diastolic left ventricular dimension index (calculated as end-diastolic dimension/cube root of body surface area) and stroke index were greater in obese patients. When the obese patients were divided into 2 groups according to the intraabdominal visceral fat area to subcutaneous fat area ratio (V/S) determined by computed tomography, the diastolic dimension index and the stroke index were significantly greater in visceral-type obesity (V/S greater than or equal to 0.4) than in subcutaneous-type obesity (V/S less than 0.4) (43.2 +/- 2.9 vs 40.3 +/- 3.1 mm/m2/3, p less than 0.01 and 49.3 +/- 6.1 vs 40.3 +/- 5.6 ml/m2, respectively). Multiple regression analysis with independent variables of age, body weight, duration of obesity and V/S ratio showed that diastolic dimension index and stroke index significantly correlated with the V/S ratio. Thus, the alteration of cardiac function in obese patients is attributable not only to excess body weight and duration of obesity but also to intraabdominal fat accumulation.

Hypocholesterolemic effect of vegetable protein in a hypocaloric diet

Eleven obese volunteers took part in a 12-week study during 8 weeks of which 2 meals of their control 1000 kcal diets were replaced by a soya based liquid formula (1 month) or a milk based liquid formula (1 month). The mean weight loss per month was 2.5 kg (P less than 0.05). On the soya formula total and LDL cholesterol levels were reduced significantly over the month by 10.0 +/- 2.7% (P less than 0.01) and 17.5 +/- 5.6% (P less than 0.02), respectively. Neither the milk based formula or the control low calorie diet lowered serum cholesterol significantly over the diet period. No change was seen in serum triglycerides on any of the 3 diets. No difference was seen between treatments in 24-h urinary C-peptide excretion. The results indicated that use of a vegetable protein supplement in a weight loss program which induced moderate weight loss was associated with a reduction in blood lipids, whereas moderate weight loss on a control low calorie diet or milk based formula was not.

Mechanisms underlying regional differences in lipolysis in human adipose tissue

Catecholamine-induced lipolysis was investigated in nonobese females and males. Isolated subcutaneous adipocytes were obtained from the abdominal and gluteal regions. The lipolytic effect of noradrenaline was four to fivefold more marked in abdominal adipocytes than in gluteal fat cells. This regional difference was more apparent in females than in males. No site differences were observed when lipolysis was stimulated with agents acting at different postreceptor levels. The beta-adrenergic lipolytic sensitivity was 10-20 times greater in abdominal adipocytes from both sexes than in gluteal adipocytes. Abdominal adipocytes from females showed a 40 times lower alpha 2-adrenergic antilipolytic sensitivity than did gluteal adipocytes, but the adenosine receptor sensitivity was similar in both sites. Beta-receptor affinity for agonists displayed no site or sex variation. Abdominal adipocytes showed a twofold increased beta-adrenoceptor density than did gluteal cells from both sexes. The alpha 2-adrenoceptor density was similar in all regions, but in females the affinity of clonidine for these sites was 10-15 times lower in the abdominal fat cells compared with gluteal cells. In conclusion, regional differences in catecholamine-induced lipolysis are regulated at the adrenoceptor level, chiefly because of site variations in beta-adrenoceptor density. Further variations in the affinity properties of alpha 2-adrenergic receptor in females may explain why the regional differences in catecholamine-induced lipolysis are more pronounced in women than in men.

Role of hepatic-triglyceride lipase activity in the association between intra-abdominal fat and plasma HDL cholesterol in obese women

Intra-abdominal fat content is an important variable in the association between regional body fat distribution and plasma high density lipoprotein (HDL) cholesterol levels. In the present study, we report on the role of plasma postheparin lipases as well as abdominal and femoral adipose tissue lipoprotein lipase activities in the association between body fat distribution and plasma lipoprotein levels. Postheparin plasma lipoprotein lipase (LPL), hepatic-triglyceride lipase (H-TGL), abdominal and femoral adipose tissue (AT)-LPL activities and plasma lipoprotein levels were measured after an overnight fast in a sample of 16 obese women (ages 36.0 +/- 6.1 years [mean +/- SD], percent body fat 46% +/- 6%). Computed axial tomography was used to assess body fat distribution. Plasma postheparin LPL activity was neither correlated with total adiposity nor with the level of intra-abdominal fat. Intra-abdominal fat deposition was, however, positively correlated with H-TGL activity (r = 0.66, p less than 0.005). Furthermore, covariance analysis showed that the association between intra-abdominal fat and H-TGL was independent from total adiposity. Plasma postheparin LPL and abdominal AT-LPL activities showed no significant correlation with plasma lipoprotein levels, whereas femoral AT-LPL activity was positively correlated with the HDL2 cholesterol/HDL3 cholesterol ratio (r = 0.51, p less than 0.05). H-TGL activity was, however, negatively correlated with HDL2 cholesterol (r = -0.60, p less than 0.05), but not with HDL3 cholesterol (r = -0.28, NS). These results suggest that the high H-TGL activity in obese women with excess deep abdominal fat could be responsible for the reduction in plasma HDL2 cholesterol levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Obesity: basic considerations and clinical approaches

Obesity, defined as an excess of body fat, can be measured with a variety of techniques, but in most epidemiologic studies it is estimated from height and weight or from skinfold thickness. The "gold standard" for body fat is the body density from which fat and fat-free body mass can be calculated. The new technique of bioelectric impedance analysis may substantially improve the estimation of total body fat. For estimating regional fat distribution, either waist to hip circumference ratio or subscapular skinfold have been most useful. Using the body mass index, defined as weight in kilograms divided by the square of the height in meters (kilogram per square meter), the National Health and Nutrition Examination Survey estimated that 26%, or 34 million, adult Americans aged 20 to 75 were overweight. The prevalence of severe overweight (a body mass index above 30 kg/m2) is higher in the United States and Canada than in Great Britain, the Netherlands, or Australia. Obesity results from an increase in energy intake relative to expenditure. Total daily energy expenditure includes energy used during resting metabolism, energy associated with the ingestion of food, and energy needed for physical activity. The obese are often observed to be less active, but since carrying a heavier load requires more energy, their total energy expenditure may not be low. A low resting metabolic rate has been suggested as a predictor of future risk of becoming obese. Adipose tissue is the major site for fat storage and may contain more than 90% of total energy stores. The increase in body mass index or degree of body weight is associated with an increased risk of heart disease, hypertension, gall bladder disease, and diabetes mellitus. When fat is centrally located in either males or females, the risk for these diseases is also increased, and may be a more important risk factor than total overweight itself. Genetic factors form the background from which obesity develops. The best estimates suggest that these genetic factors may be of less importance than environmental events in determination of total body fat and its distribution. Obesity can be classified on the basis of the total number of fat cells and regional fat distribution by using the etiological factors which caused the obesity or by determining the age at which the obesity began. Regardless of the cause, treatment for obesity should be based on an evaluation of the individual's risk from obesity as compared with the risk of the treatment under consideration. (ABSTRACT TRUNCATED AT 400 WORDS)

Importance of obesity for the metabolic abnormalities associated with an abdominal fat distribution

Obese people with a high waist/hip ratio (W/H ratio) have an increased risk for cardiovascular disease. The present study was designed to separately analyze the importance of obesity and the regional fat distribution for the metabolic risk factors. Blood pressure, glucose tolerance, insulin, and plasma lipid levels were studied in lean and obese postmenopausal women with a high or low W/H ratio. The individuals within each group were carefully matched for age, lean body mass, and body fat. The risk factors associated with a high W/H ratio (elevated blood pressure, blood lipids, and glucose levels) were found in the obese but not in the lean women. Furthermore, lean women with a high W/H ratio tended to have a lower metabolic risk factor profile than obese women with a low W/H ratio. These findings document the importance of obesity in expressing the metabolic risk factors for cardiovascular disease associated with a high W/H ratio.

The relation of body fat distribution, as assessed by six girth measurements, to diabetes mellitus in women

Independently of the amount of adipose tissue, certain patterns of fat distribution increase the risk of non-insulin-dependent diabetes. Although the ratio of waist to hip (WHR) circumferences has been consistently related to diabetes mellitus, it is possible that only two measures do not completely characterize fat topography. The current study, therefore, examines the cross-sectional relation of six girths (waist, hip, neck, bust, wrist, and ankle) to diabetes mellitus in 43,595 women. As compared with non-diabetics, Quetelet index (kg/m2) and all circumferences were elevated among diabetics. Stratified analyses showed that WHR, and waist, neck, and bust girths were consistently related to diabetes independently of the degree of overweight. As estimated from a logistic regression model that simultaneously controlled for age and all anthropometric variables, the prevalence of diabetes mellitus was positively related to Quetelet index, and to the waist, bust, and neck girths, with odds ratios (ORs) ranging from 1.4 to 2.6. However, diabetes was inversely related to hip (OR = 0.61) and ankle (OR = 0.73) girths; p less than 0.005 for each association. Although cross-sectional in nature, these results suggest that an adverse body fat distribution is not limited to the abdominal region, but that a relative preponderance of adipose tissue in various regions of the upper body is associated with diabetes mellitus in women.

Pubescence-related changes in hepatocyte insulin dynamics in female rats

Insulin binding and receptor-mediated insulin processing were investigated in isolated hepatocytes from sexually maturing female rats and from age-matched animals that had undergone prepubertal ovariectomy or whose sexual dimorphism had been disrupted by neonatal androgen treatment. Equilibrium insulin binding was determined after 18 h of incubation with 125I-TyrA14-monoiodoinsulin at 4 degrees C. Receptor-mediated insulin processing was studied after overnight binding with 100 pM insulin at 4 degrees C and subsequent incubation at 37 degrees C. Insulin binding at tracer concentrations increased 50% from sexual immaturity at 3-4 wk through pubescence at 6-8 wk and was further increased into young adulthood at 10-12 wk. Scatchard analysis indicated that the altered binding was due primarily to an increase in receptor number. Increased binding with sexual maturation resulted in correspondingly higher levels of insulin in each of the four compartments of processing studied (cell surface bound, internalized, degraded, and released). A corresponding increase in receptor-mediated insulin degradation after 10 min at 37 degrees C was observed, as changes in insulin degradation were proportional to the increase in insulin receptor binding. The age-related increase in insulin binding and subsequent increase in degradation were abolished by prepubertal ovariectomy. Furthermore, disrupting sexual dimorphism by perinatal androgen treatment resulted in a reduction of the age-related increase in insulin binding, but the percentage of insulin degraded was significantly greater than that accounted for by the increase in receptor number. As a result, insulin degradation per unit of receptor-bound hormone was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of adipose tissue in intraabdominal depots of nonobese men and women

Adipocyte size, lipoprotein lipase (LPL) activity, and the lipolytic response to noradrenaline and isoproterenol were studied in three intraabdominal depots (mesenteric, omental, retroperitoneal), as well as in subcutaneous abdominal adipose tissue, in nonobese groups of middle-aged men and in premenopausal and postmenopausal women. Subcutaneous adipocytes were larger than intraabdominal adipocytes in all groups. The men had large adipocytes in all intraabdominal depots as compared with the women. The premenopausal women seemed to have low LPL activity in intraabdominal depots. Two types of responses to catecholamine-stimulated lipolysis were observed: a similar response from mesenteric and omental (portal) fat depots and from retroperitoneal and subcutaneous abdominal (nonportal) fat depots. Young women had higher lipolysis in nonportal than in portal adipose tissues. In the men the reverse characteristics were found. These dissimilarities seem to be based on differences in beta-adrenergic responsiveness. Postmenopausal women showed no differences between depots. The differences in lipolytic responsiveness between these groups might be caused by sex steroid hormones.

Relationship of body fat distribution to metabolic complications in obese prepubertal boys: gender related differences

Our purpose was to assess the relationship of obesity and body fat distribution to serum glucose values, insulin concentration and insulin resistance in obese prepubertal boys. Thirteen obese and 15 control prepubertal boys were studied. Biceps, triceps, subscapular and suprailiac skin fold thicknesses were measured. Percentage of body fat and total body fat were calculated. Body fat distribution was assessed by analyzing the central (supra-iliac, subscapular)/peripheral (biceps, triceps) ratios. During an oral glucose tolerance test, serum glucose and insulin were measured and insulin/glucose was calculated. Body fat data and body fat distribution indices were significantly higher in the obese group. The obese population presented significantly elevated values of insulin and insulin/glucose. In the obese group insulin showed significant correlations with percentage of body fat, total body fat and subscapular skin fold thickness, whereas insulin/glucose had significant positive correlations with percentage of body fat, total body fat and supra-iliac skin fold thickness. In obese boys significant positive correlations were also shown by subscapular/supra-iliac with insulin and insulin/glucose, and by subscapular/triceps with insulin. In prepubertal boys obesity is centripetal and an upper central body fat distribution seems to be first associated with an abnormal glucose-insulin homeostasis.

Influence of body fat distribution on free fatty acid metabolism in obesity

In order to determine whether differences in body fat distribution result in specific abnormalities of free fatty acid (FFA) metabolism, palmitate turnover, a measure of systemic adipose tissue lipolysis, was measured in 10 women with upper body obesity, 9 women with lower body obesity, and 8 nonobese women under overnight postabsorptive (basal), epinephrine stimulated and insulin suppressed conditions.

RESULTS

Upper body obese women had greater (P less than 0.005) basal palmitate turnover than lower body obese or nonobese women (2.8 +/- 0.2 vs. 2.1 +/- 0.2 vs. 1.8 +/- 0.2 mumol.kg lean body mass (LBM)-1.min-1, respectively), but a reduced (P less than 0.05) net lipolytic response to epinephrine (59 +/- 7 vs. 79 +/- 5 vs. 81 +/- 7 mumol palmitate/kg LBM, respectively). Both types of obesity were associated with impaired suppression of FFA turnover in response to euglycemic hyperinsulinemia compared to nonobese women (P less than 0.005). These specific differences in FFA metabolism may reflect adipocyte heterogeneity, which may in turn affect the metabolic aberrations associated with different types of obesity. These findings emphasize the need to characterize obese subjects before studies.

Gall stones in a Danish population. Relation to weight, physical activity, smoking, coffee consumption, and diabetes mellitus

The presence of gall stones diagnosed by ultrasonography in a cross sectional study was analysed in relation to relative weight, weight change since age 25, slimming treatment, physical activity, smoking, consumption of coffee, and diabetes mellitus. The random sample comprised 4581 men and women of Danish origin, aged 30, 40, 50, and 60 years, of whom 3608 (79%) attended the investigation. In women high body mass index, history of slimming treatment, and weight gain since the age of 25 of more than 5 body mass index units were each significantly associated with gall stones (p less than 0.05), while only body mass index was significant (p less than 0.05) in a multivariate analysis. In men history of slimming treatment was significantly associated (p less than 0.05) with gall stones in univariate and in multivariate analyses, where smoking also became significantly associated (p less than 0.05). No significant association was detected between gall stones and the other variables.

Adipose tissue distribution and plasma lipoprotein levels in obese women. Importance of intra-abdominal fat

Prospective studies have shown that excess abdominal fat is associated with an increased risk of coronary heart disease and related death. We used computed axial tomography (CAT) to assess the association between deep and subcutaneous abdominal adipose tissue and plasma lipoprotein levels in a sample of 52 premenopausal obese women aged 35.7 +/- 5.5 years (mean +/- SD). Whereas the plasma lipoprotein concentration were not significantly correlated with fat mass, the data obtained by CAT indicated that the absolute amount of deep abdominal fat was negatively correlated with high density lipoprotein cholesterol (HDL-CHOL) levels (r = -0.35, p less than 0.01), as well as with HDL-CHOL/low density lipoprotein (LDL)-CHOL, HDL-apoprotein-(apo) A-I/LDL-apo B, and HDL2-CHOL/HDL3-CHOL ratios (-0.32 less than or equal to r less than or equal to -0.40, 0.05 greater than p less than 0.01). Adipose tissue deposition at the mid-thigh region determined by CAT did not show any significant relationship with plasma lipoprotein levels. When subgroups of women with comparable ages and adiposity but with high and low intra-abdominal fat accumulation were compared, women with a high accumulation of intra-abdominal fat displayed significantly lower HDL-CHOL (p less than 0.001), HDL2-CHOL (p less than 0.001), HDL3-CHOL (p less than 0.01), and HDL-apo A-I (p less than 0.05) levels, as well as reduced HDL-CHOL/LDL-CHOL (p less than 0.01), HDL-apo A-I/LDL-apo B (p less than 0.05), and HDL2-CHOL/HDL3-CHOL ratios (p less than 0.05) in comparison with obese women with low accumulations of intra-abdominal fat.(ABSTRACT TRUNCATED AT 250 WORDS)

Biology of regional body fat distribution: relationship to non-insulin-dependent diabetes mellitus

Our studies support the view that body fat distribution and the accompanying metabolic abnormalities could be exacerabated by variability in the androgenic/estrogenic balance. Sensitivity to the androgenic milieu might be initiated by an early developmental aberration in sexual dimorphism. The possible direct and indirect sites of interaction between androgenic activity and the abnormal metabolic pathways in upper body obesity are summarized in Figure 19.

Obesity, metabolism, and hypertension

The relationship between obesity and hypertension is complex and poorly understood. A developing body of information suggests that metabolic factors related to the obese state are importantly involved. The pertinent observations include: (1) Diet influences sympathetic nervous system activity. Fasting suppresses, while carbohydrate and fat feeding stimulate, sympathetic activity. (2) Dietary-induced changes in sympathetic activity contribute to the changes in metabolic rate that accompany changes in dietary intake. (3) Insulin-mediated glucose metabolism in the hypothalamus provides a link between dietary intake and sympathetic nervous system activity. And (4) hyperinsulinemia, a consequence of insulin resistance in the obese, is associated with hypertension. These observations have suggested the following hypothesis. Hyperinsulinemia results in sympathetic stimulation which drives thermogenic mechanisms, thereby increasing metabolic rate. The net result is a restoration of energy balance at the expense of hyperinsulinemia and increased sympathetic activity. Hypertension is thus the unfortunate consequence of hyperinsulinemia, which increases renal sodium reabsorption, and sympathetic stimulation of the heart, kidney, and vasculature. The data on which this hypothesis is constructed are reviewed and the implications discussed.

Classification and evaluation of the obesities

Obesity is a condition of multifactorial etiology that can be associated with important health and functional consequences. Suggestions for the proper evaluation of obese patients have been presented along with brief descriptions of the rationales for their use. The evaluation protocol has been summarized in two algorithms to aid in the performance of a complete and organized work-up.

Association of decreased sex hormone binding globulin and cardiovascular risk factors

Sex hormones play a major role in determining the risk of cardiovascular disease. While earlier studies have shown that reduced sex hormone binding globulin (SHBG) is associated with increased glucose and insulin concentrations in premenopausal women, few data exist on the relationship of SHBG to other cardiovascular risk factors in women. We hypothesized that decreased SHBG would be associated with an atherogenic pattern of cardiovascular risk factors. We measured total testosterone, total estradiol and SHBG, lipids and lipoproteins, glucose and insulin, and systolic and diastolic blood pressure in 96 premenopausal women. Although total testosterone and total estradiol were not related to cardiovascular risk factors, SHBG was negatively associated with triglyceride concentration (r = -0.37) and positively associated with high density lipoprotein cholesterol (HDLC) (r = 0.42). After adjustment for overall adiposity (body mass index) and upper body adiposity (as measured by the ratio of waist-to-hip circumferences), SHBG was still positively related to HDLC, but not to triglyceride. Adjustment for insulin abolished the relationship between SHBG and triglyceride levels, but did not alter the relationship between SHBG and HDLC. Sex hormones were not related to either systolic or diastolic blood pressure.

Diagnosis and prevalence of obesity

Obesity is a condition of increased adipose tissue mass. Many techniques are available for measurement of body fat, but none is available widely for clinical purposes. The new technique of bioelectrical impedance may change this in the future. For now, relative weight and BMI are used as indices of obesity, which may be defined as a BMI greater than 30 kg per m2. This corresponds to a relative weight approximately 120 per cent above desirable. According to this definition, obesity exists in 10 to 12 per cent of adult men and women in the United States and Canada.

Relationships between serum testosterone, fasting insulin and lipoprotein levels among elderly men

We have previously reported the existence of an association between endogenous male sex hormone and lipoprotein levels in elderly men confined to a nursing home. In a further attempt to elucidate the significance of the association mentioned, we studied the relationship existing in that population between serum testosterone and fasting insulin levels, and between fasting insulin level and lipoprotein pattern. The data were analysed by means of stepwise multiple regression analyses. Serum testosterone and fasting insulin were found to be strongly correlated; this is consistent with the notion that androgen secretion affects directly circulating insulin level. But no independent relationship was demonstrable between fasting insulin and the three lipid-lipoprotein categories studied, namely total serum cholesterol, triglyceride and HDL-cholesterol, suggesting that in this particular population, the effect of male sex hormones upon lipoproteins is not mediated through insulin. Together, these various observations support the belief that androgen secretion affects significantly CAD risk factor levels in elderly men.

Health risks of obesity

Evidence implicating obesity as a risk-factor disease is critically reviewed. Possible reasons for the many conflicting findings are addressed. The classification of obesity, based upon the site of body fat distribution, and possible biologic mechanisms associating regional adiposity with morbidity, are discussed.

Effects of exercise training on high density lipoproteins and apolipoprotein A-I in old and young men

Although exercise training has been demonstrated to improve lipid profiles in young and middle-aged subjects, the response in training in the elderly has received little attention. In this study, we assessed and compared the changes in aerobic capacity, lipid profiles, and body composition in young (Y, 31.9 +/- 5.5 years; n = 18) and older (O, 65.1 +/- 6.1 years; n = 10) subjects in response to similar 3-month exercise training programs (80% to 85% of heart rate reserve, three times per week). We hypothesized that the responses would be qualitatively similar for the two groups, although the absolute quantitative response might be somewhat less in the elderly. The two groups were quite similar at baseline for percent body fat (Y, 30.1% +/- 7.2% v O, 30.3% +/- 4.7%; P = NS) and maximal aerobic capacity (Y, 36.8 +/- 8.1 v O, 36.3 +/- 8.3 mL/kg/min; P = NS). In addition, there were no significant differences in the baseline lipid profiles between the groups. After training, the improvements in body composition were similar, with both groups losing similar amounts of fat (Y, 2.86% +/- 3.14% v O, -2.85% +/- 1.78%) and neither group significantly changing their fat-free mass. Maximal aerobic capacity improved in both groups, but the increment was greater in the young (18% v 10%, P less than .05). HDL-cholesterol (+6%, P less than .01) and apolipoprotein A-I (+6%, P less than .01) concentrations increased significantly only in the young. These increments, however, were not different from those observed in the older subjects (+7% and +4%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Increased insulin concentrations in nondiabetic offspring of diabetic parents

Insulin resistance is thought by many to be the primary defect that results in non-insulin-dependent diabetes mellitus (NIDDM). An implication of this theory is that prediabetic persons have higher serum insulin levels than normal subjects. We assessed serum insulin concentrations in a cohort of 1497 nondiabetic Mexican Americans, a population at high risk for NIDDM, according to whether their parents or siblings had diabetes. It was assumed that prediabetic persons would be more likely to have strong family histories of diabetes. We found a stepwise increase in fasting insulin levels in nondiabetics with neither, one, or both parents with diabetes (69.8, 77.8, and 94.6 pmol per liter, respectively; P = 0.002). Similar results were observed for insulin sum (the total of insulin concentrations in the fasting state and at 30, 60, and 120 minutes after a 75-g oral glucose load). The differences in insulin sums according to family history remained statistically significant in analyses of covariance, which controlled for variations in body-mass index, body-fat distribution, and level of blood glucose. Subjects without diabetes who had a diabetic sibling had higher fasting concentrations of insulin than subjects without a diabetic sibling (83.2 vs. 69.6 pmol per liter), but the difference was not statistically significant. We conclude that prediabetic persons, who would be expected to be more numerous in kindreds with progressively stronger family histories of diabetes, have hyperinsulinemia. This supports the insulin-resistance hypothesis.

Diabetes, hyperinsulinaemia, and coronary risk factors in Bangladeshis in east London

Immigrants from the Indian subcontinent (South Asians) in England and Wales have higher morbidity and mortality from coronary heart disease than the general population; this seems to apply to both Hindus and Muslims. Studies in north west London and Trinidad found that the increased risk of coronary heart disease in Indians was not explained by dietary fat intakes, smoking, blood pressure, or plasma lipids. In the present study the distribution of coronary risk factors was measured in an East London borough where the mortality and attack rate from coronary heart disease are higher in the Asian population, predominantly Muslims from Bangladesh, than in the rest of the population. In a sample of 253 men and women aged 35-69 from general practice, mean plasma cholesterol concentrations were lower in Bangladeshi than in European men and women. Mean systolic blood pressures were 10 mm Hg lower in Bangladeshis. Plasma fibrinogen concentrations were similar in Bangladeshis and Europeans and factor VII coagulant activity was lower in Bangladeshi than in European men. In contrast with the findings in Hindus in north west London, smoking rates were high in Bangladeshi men and the ratio of polyunsaturated fatty acids to saturated fatty acids in plasma lipids was lower in Bangladeshis than in Europeans. Diabetes was three times more common in Bangladeshis than in Europeans and serum insulin concentrations measured after a glucose load were twice as high in Bangladeshis. High insulin concentrations in Bangladeshis were associated with high plasma triglyceride and low high-density lipoprotein cholesterol concentrations. Insulin resistance, leading to diabetes, hyperinsulinaemia, and secondary lipoprotein disturbances, is a possible mechanism for the high rates of coronary heart disease in South Asians in Britain and overseas.

Obesity. Part I--Pathogenesis

Obesity--defined by a body mass index above 30 kg per m2--is a major problem for affluent nations. Its prevalence is higher in North America than in Europe--between 9% and 12% of the population. Reduced energy expenditure from exercise or metabolism or both may be an important contributory factor in the development of obesity because of a failure to reduce food intake sufficiently to maintain energy balance. A high ratio of abdominal circumference relative to gluteal circumference carries a twofold or greater risk of heart attack, stroke, hypertension, diabetes mellitus, gallbladder disease, and death. The effect of increased quantities of abdominal fat is greater than that of a similar increase in total body fat on the risks of ill health associated with obesity. Genetic factors appear to contribute about 25% to its etiology.

Measures of fat distribution as determinants of serum lipids in healthy volunteers consuming a uniform standardized diet

The relation was investigated between body fat topology and serum lipoproteins in healthy, nonobese men and women. Twenty-four men and 24 women consumed a standardized affluent diet for 17 days. Serum was obtained after 14 and 17 days. Regression coefficients of lipids and lipoproteins with age, body mass index, measures of fat distribution, and estimates of fat areas at a cross-section of the body at the level of the umbilicus, were calculated. Waist-to-thigh circumference ratio proved to be the strongest correlate of serum lipids compared with other measures of fat distribution. Upon multiple regression analysis, the waist-to-thigh ratio proved to be a stronger predictor of total cholesterol, LDL-cholesterol and triglyceride levels in men than either age or body mass index. In women this was only true for HDL3-cholesterol. In addition, no significant relations were observed any more of age and body mass index with these serum lipids, with the exception of age for IDL-cholesterol in men. Estimates of intra-abdominal fat area showed in general a stronger correlation with serum lipids than estimates of subcutaneous fat area. It is concluded that, in non-obese subjects, fat distribution is a stronger determinant of serum lipids than either body mass index or age.

Aetiology. Non-insulin-dependent diabetes

NIDDM appears to be a disease of complex aetiology. Although specific genetic markers for the disease have yet to be defined, there is clear evidence for genetic predisposition, with high concordance in monozygous twins. However, concordance is incomplete, and there are therefore additional, non-genetic, mechanisms which are responsible for increasing the risk of the disease in susceptible subjects. At the present time, the most plausible environmental precipitants appear to be the inter-related triad of obesity, low levels of habitual physical exercise and diet. The power of environmental determinants, and their interaction one with another, may also be subject to individual genetic determination, and may not act in a similar manner in all populations. Some non-Caucasian populations, which have undergone marked sociocultural change, are now extremely susceptible to NIDDM. This is probably the result of evolutionarily heightened genetic predisposition, compounded by strong environmental influence resulting from the recent changes in their human ecology. Since prevalence is strongly related to age, NIDDM also represents a growing problem to the world's industrialized societies, for many of which longevity is now the major demographic trend. Research into the aetiology of NIDDM must not only continue, it must also explore new directions, and attain greater scientific depth and sophistication, if it is to make a useful contribution to the eventual prevention and control of the disease.

Excess body fat distribution and glucose homeostasis in obese Arab women

The relationship of body fat distribution to glucose intolerance and non-insulin-dependent diabetes mellitus in Arab women was studied in 102 obese non-diabetic and 40 obese women with diabetes. The obese women underwent a glucose tolerance test. Linear regression analysis revealed a significant correlation between the waist/hip ratio and the plasma glucose concentration at 120 min. When divided into two groups according to the median of their waist/hip ratio (0.815), obese women without history of diabetes but with high waist/hip ratio (0.86 +/- 0.07, mean +/- SD) had significantly higher prevalence of glucose intolerance and of diabetes mellitus than those with the low ratio (0.78 +/- 0.03, chi 2 = 9.32, p less than 0.001). The highest ratio (0.89 +/- 0.06) was observed in the obese women with known diabetes mellitus.

Hyperinsulinemia, upper body adiposity, and cardiovascular risk factors in non-diabetics

Previous studies have suggested that hyperinsulinemia and upper body adiposity are each separately associated with elevated BP and triglyceride (TG) levels, and with lower high density lipoprotein (HDL) cholesterol levels. The joint effect of hyperinsulinemia and upper body adiposity on lipids, lipoproteins, and BP, however, has not been previously studied. We hypothesized that the effect of body fat distribution on cardiovascular risk factors might be mediated through hyperinsulinemia. We measured BP, lipids and lipoproteins, HDL subfractions, and insulin and glucose concentrations as part of the San Antonio Heart Study, a population-based study of diabetes and cardiovascular risk factors. Insulinemia and glycemia were assessed as the sum of the fasting, half-hour, one-hour, and two-hour insulin and glucose levels, respectively, measured during a standardized oral glucose tolerance test. Individuals who had diabetes according to National Diabetes Data Group criteria were excluded from the analyses. In univariate analyses, both hyperinsulinemia and waist-to-hip ratio (WHR), a measure of upper body adiposity, were positively associated with TG and negatively associated with total HDL and HDL2 cholesterol levels. However, when the effects of glycemia and insulinemia were controlled for by analysis of variance, WHR was no longer significantly related to TG levels. By contrast, WHR continued to be inversely related to total HDL and HDL2 cholesterol even after adjustment for glycemia and insulinemia. Hyperinsulinemia was only weakly related to HDL cholesterol. These results suggest that insulinemia and glycemia might mediate the effects of upper body adiposity on TG, although not on HDL and HDL2 cholesterol. Hyperinsulinemia was also positively associated with diastolic and systolic BP in men.

Regional adipocyte precursors in the female rat. Influence of ovarian factors

A flow cytometric immunofluorescence procedure utilizing a specific antibody to rat adipose tissue lipoprotein lipase (LPL) was developed to quantify differentiated and undifferentiated preadipocytes present in the adipose tissue vascular stroma. This method is highly sensitive and specific for cells capable of synthesizing LPL in significant quantities. Pubescence in female rats was associated with an increase in differentiated preadipocytes and in fat cell number with enlargement of the fat depots in the perirenal, parametrial, and the subcutaneous dorsal and femoral regions. A concomitant decline in the percentage of undifferentiated preadipocytes occurred in all but the femoral depot. Ovariectomy reduced pubertal adipose growth in the femoral and parametrial but not the dorsal or perirenal regions. Furthermore, the femoral undifferentiated preadipocyte pool was not preserved in the ovariectomized animals. Thus, ovarian factors influence the pubescence-associated regional preadipocyte differentiation and conversion to adipocytes. The femoral depot contains an ovarian-dependent infinite pool of fat cell precursors. These features could account for the association between ovarian hormones and body fat topography.

Fat distribution, endocrine and metabolic profile in obese women with and without hirsutism

The relationship between adipose tissue distribution, androgen levels, and metabolic complications of obesity was studied in 20 hirsute and 20 nonhirsute obese premenopausal women. The group of hirsute women showed preferentially an upper body type of obesity as assessed by the waist-to-hip ratio (0.902 + 0.017 v 0.778 +/- 0.015, P less than .01). They had higher serum concentrations of total testosterone (100.4 + 11.7 v 48.8 +/- 4.5 ng/dL, P less than .01) and lower levels of serum sex-hormone-binding globulin (28.1 +/- 3.6 v 44.0 + 4.2 nmol/L, P less than .05) exhibiting an increased androgenic activity as compared to the nonhirsute women. Serum glucose and insulin levels after an oral glucose load were significantly higher in the hirsute women. In addition, the group of hirsute females has significantly higher fasting concentrations of total cholesterol (5.82 +/- 0.28 v 4.75 +/- 0.14 mmol/L, P less than .05) and triglycerides (2.51 +/- 0.38 v 1.14 +/- 0.10 mmol/L, P less than .01). The hirsute group also showed higher systolic (166.7 +/- 5.1 v 142.1 +/- 4.5 mm Hg, P less than .01) and diastolic (100.9 +/- 3.6 v 85.2 +/- 2.5 mm Hg, P less than .01) blood pressure values than the nonhirsute women. Analysis of correlation revealed that an increasing waist-to-hip ratio was accompanied by increasing testosterone levels (r = .39, P less than .05) and by decreasing sex-hormone-binding globulin levels (r = .37, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

[Relation between body fat distribution, insulin levels and glucose tolerance in obese females]

Relationship between body fat distribution, serum insulin, and glucose tolerance in obese, non-diabetic women. Recent studies suggest that hyperinsulinemia and upper body obesity are predictive factors for the development of non-insulin-dependent diabetes mellitus. To further characterize the relationship between body fat distribution, serum insulin, and glucose tolerance an oral glucose tolerance test was performed in 48 obese, non-diabetic women. Fasting insulin levels were correlated to both total body fat calculated as body mass index (r = 0.58, p less than 0.001) and upper body fat distribution expressed as waist-to-hip ratio (WHR, r = 0.47, p less than 0.01). In the women with upper body fat localization (WHR greater than 0.90) significantly higher basal and glucose-stimulated insulin concentrations were established than in the women with a lower body type of obesity (WHR less than 0.78) (basal insulin 27.4 +/- 11.5 vs. 15.4 +/- 8.8 mU/l, p less than 0.05, insulin area 779 +/- 320 vs. 468 +/- 237 U, p less than 0.05). They also had impaired glucose tolerance (glucose area 925 +/- 139 vs. 633 +/- 147 U, p less than 0.01). Fasting triglyceride concentrations were correlated both with WHR (r = 0.63, p less than 0.001) and fasting insulin (r = 0.33, p less than 0.05) but not with BMI (r = -0.02, n.s.). A positive association was found between systolic and diastolic blood pressure and both WHR (r = 0.43 and r = 0.44 resp., p less than 0.01) and BMI (each r = 0.35, p less than 0.05). Interestingly, basal insulin was also associated with blood pressure (r = 0.30, p less than 0.1, and r = 0.40, p less than 0.01 resp.).(ABSTRACT TRUNCATED AT 250 WORDS)

Body fat distribution, plasma lipids, and lipoproteins

The relation of body fat distribution as measured by the ratio of waist to hip circumferences (WHR) to plasma levels of lipids and lipoproteins was studied in 713 men and 520 women who were employed by two Milwaukee companies. Quetelet index (kg/m2), waist girth, hip girth, and WHR were each positively related to levels of total cholesterol, triglycerides, apolipoprotein B, and the ratio of total to high density lipoprotein (HDL) cholesterol. In addition, the anthropometric measures were inversely associated with levels of HDL cholesterol. (Controlling for age, alcohol intake, exercise level, current smoking status, and oral contraceptive use only slightly reduced the strength of the correlations.) In addition, WHR and Quetelet Index were independently related to lipid and lipoprotein levels, and the magnitudes of the associations were roughly equivalent. For example, the mean (covariate-adjusted) triglyceride level among men in the upper tertile of the Quetelet Index was 37 mg/dl higher than for men in the lower tertile of the Quetelet Index; the corresponding difference according to WHR tertiles (upper to lower) was 39 mg/dl (p less than 0.01 for both effects). These findings indicate that in healthy men and women a less favorable lipid and lipoprotein profile is associated with elevated levels of both Quetelet Index and WHR.

Association of body fat distribution with plasma lipids, lipoproteins, apolipoproteins AI and B in postmenopausal women

Associations between the distribution of body fat, measured by the waist/hip circumference ratio (WHR), and plasma lipid fractions were examined in 84 postmenopausal women. WHR was correlated r = 0.39 with body mass index (BMI). After adjustment for BMI and other covariates, WHR was positively and significantly associated with concentrations of triglycerides, apolipoprotein B, low-density lipoprotein cholesterol, and the total cholesterol/high density lipoprotein cholesterol ratio. WHR was negatively and significantly associated with concentrations of high density lipoprotein cholesterol and apolipoprotein AI. These results indicate that in postmenopausal women abdominal fat preponderance is associated with an atherogenic plasma lipid profile, independent of its association with BMI.

A weight shape index for assessing risk of disease in 44,820 women

The medical literature gives ample evidence of the relationship between obesity and specific diseases such as adult-onset diabetes and hypertension. Until recently the sole focus of the relationship has been between morbidity and the degree of overweight which is usually measured as weight relative to height. Recently we have shown that the location of body fat is not only associated with morbidity but that this relationship is independent of the total amount of adipose tissue. Clinical studies have shown that adipocyte size, location and metabolism are related to fat distribution. An excess of large fat cells in the upper body explains the increase risk of diabetes in women. The location of body fat has been used to delineate three body types: gynoid (pear shape), intermediate, and android (apple shape). We used waist girth divided by hip girth for scaling body shape and found that it is associated with morbidity after adjustment for relative weight. The use of relative weight and body shape simultaneously gives a better estimate of risk of morbidity than either alone. This study of 44,820 women presents easy to read graphs, derived from the multiple logistic model, which will permit practicing physicians to estimate visually the combined risks associated with relative weight and body fat location.

Influence of obesity on morbidity and mortality after acute myocardial infarction

The influence of being overweight or obese on hospital and late (1 year) mortality and reinfarction was studied in 1760 patients with acute myocardial infarction. Body mass index (BMI) was used to categorize patients as normal weight (BMI less than 25), overweight (BMI 25 to 30), and obese (BMI greater than 30). Clinical features and prognosis were compared in 658 normal weight patients, 884 overweight patients, and 218 obese patients. Complications during hospitalization and 1-year reinfarction rates following discharge were similar among the weight subsets. Hospital mortality was 13% in obese patients, similar to the 14% hospital mortality in normal weight patients, but significantly more than that in overweight patients (9%, p less than 0.05). When stratified according to age, 30% of obese patients greater than or equal to 65 years died in the hospital, compared to 13% of overweight patients (p less than 0.001), and 17% of normal weight patients (p less than 0.01). In patients less than 65 years, the obese group had a 6% mortality compared to a hospital mortality of 5% in overweight and 8% in normal weight groups (NS). In a multivariate analysis, obesity was an independent predictor of hospital death in the older, but not in the younger patient subset. One-year mortality for patients discharged from the hospital was significantly less in obese than in normal weight patients (7% vs 13%, p less than 0.05), but not different from the 11% mortality rate in overweight patients. Differences in mortality disappeared when patients were age stratified.(ABSTRACT TRUNCATED AT 250 WORDS)

Controversies in plastic surgery: suction-assisted lipectomy (SAL) and the hCG (human chorionic gonadotropin) protocol for obesity treatment

The advent of SAL (suction-assisted lipectomy) has dramatically increased the number of obese patients coming to our consultation offices. Despite several articles suggesting a conservative approach to fat suction, some reports insinuate that SAL might be a useful tool for obesity treatment. This hypothesis is refuted by a vast body of evidence that concludes that the adipose tissue may regenerate in adult humans. Therefore, surgical procedures are not advised as the method of choice to manage the disease. On the other hand, the terms obesity and being overweight may not be interchangeable. Obesity may be a disease whereas being overweight is a sign of the disease. Consequently, proper preoperative selection of candidates for SAL becomes mandatory. The hCG (human chorionic gonadotropin) method for obesity treatment appears to be a complete program for the management of obesity. It contains pharmacologic, dietetic, and behavior modification aspects in a 40-day course of treatment. Some data suggest hCG to be lipolytic, thus explaining former clinical observations regarding body fat redistribution in treated patients. hCG commercial preparations contain beta-endorphin, an opioid peptide linked to mood behavior. This article speculates on the possible actions of the complex hCG beta-endorphin in the neuromodulation of mood and energy metabolism. The method comprises a behavior modification that helps in handling the patient better. There are some correlations between a current behavior modification program and the basic guidelines contained in the hCG protocol. Thus, the hCG method appears to be a reasonable alternative in the management of a long-standing, unsolved problem of human metabolism.

Glucose uptake in human adipose tissue

One hundred grams of glucose with 50 microCi U-14C-glucose were given orally to 17 women with widely varying amounts of body fat. Radioactivity and glucose metabolism in vitro were then measured in adipose tissue obtained by needle biopsies in the abdominal and femoral regions after four hours. Radioactivity in triglycerides was then measured in repeated biopsies 1 day, 1 week, and monthly up to 7 months after glucose administration. Glucose label in triglycerides after four hours was higher in abdominal than femoral adipocytes in obese women. It increased slightly during the following week, and then decreased exponentially with a half-life of 12 months in the abdominal region and 19 months in the femoral region. Uptake of glucose carbon in total body fat was estimated from the triglyceride label measured and determinations of body fat mass, and found to be in the order of less than 4% of given glucose. The studies in vitro suggested that much of the glucose taken up in adipose tissue is converted to lactate. If this is the case in vivo, then glucose uptake in adipose tissue might well be of significance for total body glucose homeostasis, particularly in obese subjects, amounting to maximally perhaps one third to one half of the oral glucose given. The majority of this glucose uptake would then, however, leave adipose tissue again as lactate. The shorter half-life of label in abdominal adipocytes is in agreement with findings of increased lipolysis in these adipocytes in vitro.

Effect of intestinal factors on extraction of insulin in perfused rat liver

To study the direct effect of intestinal factors on hepatic extraction of insulin, an investigation was made into the extraction of insulin from isolated rat liver perfused with portal venous effluent (PVE) obtained from the isolated perfused rat intestine. Rat intestine was perfused with Krebs-Ringer bicarbonate medium for 45 min, and the PVE was collected from glucose-, lipid-, or NaCl-treated and untreated control intestines. The PVE, after adjustment of its glucose (180 mg/dl) and insulin (200 microU/ml) concentrations, was used as the perfusing medium for the liver of a different rat. The liver was perfused without recirculation with the PVE not containing insulin for 15 min and then perfused with the PVE containing insulin for the next 30 min. Insulin removal from liver perfused with PVE from lipid- or NaCl-treated intestine (52.6 +/- 5.4 or 46.6 +/- 4.1%) was similar to that from comparable controls (49.7 +/- 2.8 or 48.2 +/- 2.9%), respectively. However, that from glucose-treated intestine (39.7 +/- 6.2%) was significantly (P less than 0.01) lower than that from control intestine (51.1 +/- 2.5%). These results indicate that an intestinal factor secreted after glucose ingestion significantly reduces hepatic extraction of insulin and that at least a part of the incretin phenomenon is due to a decreased hepatic extraction of insulin after oral glucose administration.

Adipose tissue development: the role of precursor cells and adipogenic factors. Part I: Adipose tissue development and the role of precursor cells

Obesity is regarded as a heterogeneous syndrome, which may appear in different forms. Various causes have been found to contribute to its pathogenesis. During recent years investigations of adipose tissue cellularity and its dynamic changes have gained growing interest. An important progress was the discovery of adipose tissue precursor cells. These cells have not yet been precisely identified by morphological and biochemical methods in intact tissue. However, due to methodological developments such precursor cells can be cultured both as primary cultures and as established cell lines. These culture systems have proven to be valuable models for the study of the processes involved in the formation of new fat cells.