Showing papers on "Abdominal obesity published in 1999"

Hypertriglyceridemia, insulin resistance, and the metabolic syndrome.

Abstract: The metabolic syndrome consists of a cluster of metabolic disorders, many of which promote the development of atherosclerosis and increase the risk of cardiovascular disease events. Insulin resistance may lie at the heart of the metabolic syndrome. Elevated serum triglycerides commonly associate with insulin resistance and represent a valuable clinical marker of the metabolic syndrome. Abdominal obesity is a clinical marker for insulin resistance. The metabolic syndrome manifests 4 categories of abnormality: atherogenic dyslipidemia (elevated triglycerides, increased small low-density lipoproteins, and decreased high-density lipoproteins), increased blood pressure, elevated plasma glucose, and a prothrombotic state. Various therapeutic approaches for the patient with the metabolic syndrome should be implemented to decrease the risk of cardiovascular disease events. These interventions include decreasing obesity, increasing physical activity, and managing dyslipidemia; the latter may require the use of pharmacotherapy with cholesterol-lowering and triglyceride-lowering drugs.

Hypothalamic arousal, insulin resistance and Type 2 diabetes mellitus.

Abstract: Summary Aims Type 2 diabetes mellitus (DM) develops when insulin resistance overcomes the capacity of compensatory insulin secretion. Insulin resistance may be induced via psychoneuroendocrine pathways, a possibility which has received little previous attention. Methods We have used salivary cortisol measurements to monitor the activity of the hypothalamic–pituitary–adrenal (HPA) axis, the major controller of hormones involved in the regulation of peripheral insulin sensitivity under everyday conditions. The influence of external challenges, as well as the sensitivity of feedback regulation, were followed in randomly selected middle-aged population samples. Results In health there is a rhythmicity of cortisol secretion, with a high plasticity and efficient feedback control. In contrast, a group of subjects were identified with a flat, rigid day curve and poor feedback control, who showed consistent abnormalities in stress-related cortisol secretion, including inhibited secretions of sex steroids and growth hormone; insulin resistance; abdominal obesity; elevated leptin levels; hyperglycaemia; dyslipidaemia and hypertension with elevated heart rate. The endocrine abnormalities are probably responsible for the anthropometric and metabolic abnormalities. The circulatory perturbations seem to be induced by a parallel activation of the central sympathetic nervous system suggesting an ‘hypothalamic arousal syndrome’, gradually developing into an independent risk for disease. An associated cluster of environmental factors, including psychosocial and socio-economic stress, traits of depression and anxiety, alcohol consumption and smoking, all factors known to activate hypothalamic centres, has been identified. A polymorphism of the glucocorticoid receptor gene, with 13.7% homozygotes in the male Swedish population, parallels receptor dysfunction, and may be responsible for the associated insulin resistance, central obesity and hypertension. Conclusions This is the first detailed examination of psychoneuroendocrinological processes in the natural environment on a population basis in relation to somatic health. The results suggest that an hypothalamic arousal syndrome, with parallel activation of the HPA axis and the central sympathetic nervous system, is responsible for development of endocrine abnormalities, insulin resistance, central obesity, dyslipidaemia and hypertension, leading to frank disease, including Type 2 DM. We suggest that this syndrome is probably based on environmental pressures in genetically susceptible individuals. Diabet. Med. 16, 373–383 (1999)

Smoking and abdominal obesity: risk factors for venous thromboembolism among middle-aged men: "the study of men born in 1913".

Abstract: Background Risk factors for deep vein thrombosis and pulmonary embolism are mostly derived from case-control studies of hospitalized patients, and there are few long-term population-based studies. Objective To study the long-term risk factors for deep vein thrombosis and pulmonary embolism among middle-aged men. Design A prospective cohort study. Setting General community, "The Study of Men Born in 1913." Subjects A random population sample of 855 men, all aged 50 years at baseline. Main Outcome Measures Eight-hundred fifty-five men participated in a screening examination in 1963 at the age of 50 years, and 792 of these men were reexamined in 1967 at the age of 54. All the men were followed up with periodic examinations until the age of 80. Objective methods were used to ascertain a diagnosis of deep vein thrombosis or pulmonary embolism. Results Waist circumference ( P =.004) and smoking ( P =.02) predicted a venous thromboembolic event in multivariate survival analysis. Men in the highest decile of waist circumference (≥100 cm) had an adjusted relative risk of 3.92 (95% confidence interval, 2.10-7.29; P P =.009) compared with nonsmokers. Conclusions Smoking and abdominal obesity were independent risk factors for venous thromboembolic events during follow-up. In addition to the prevention of smoking and obesity, a more aggressive strategy regarding the use of prophylactic agents among smokers and obese patients, in various risk situations, may be justified.

Circulating tumor necrosis factor alpha concentrations are higher in abdominal versus peripheral obesity.

Abstract: Fat tissue is a significant source of endogenous tumor necrosis factor alpha (TNFalpha), the pluripotent cytokine that plays an important role as a mediator of the peripheral insulin resistance found in obesity. The majority of evidence for this role of TNFalpha is from studies in animal models of obesity. To explore further the role of TNFalpha in the pathogenesis of obesity-related insulin resistance in humans, we compared plasma levels of TNFalpha and the other main endocrine cytokine, interleukin-6 ([IL-6] both measured by enzyme-linked immunosorbent assay), in 26 obese women (body mass index [BMI] > 30 kg/m2) and 13 female controls (BMI < 26 kg/m2) without a history of recent or active infection. Glucose and insulin levels were measured at 0, 1, and 2 hours after a 75-g oral glucose load. There was no significant difference in plasma TNFalpha or IL-6 levels between obese and non-obese subjects overall (2.10 +/- 0.19 v 1.65 +/- 0.18 pg/mL and 2.06 +/- 0.29 v 1.50 +/- 0.17 pg/mL, respectively). However, TNFalpha levels were significantly elevated in obese subjects with a 2-hour glucose level more than 140 mg/dL (n = 8) compared with the other obese subjects (n = 18) and the non-obese controls (2.88 +/- 0.46 v 1.75 +/- 0.10 and 1.65 +/- 0.18 pg/mL, respectively, P < .01). Furthermore, the TNFalpha level correlated significantly with the waist to hip ratio ([WHR] r = .53, P < .01) and fasting and post-oral glucose tolerance test (OGTT) insulin levels (r = .47, P < .02), but not with the BMI, and was higher in obese women with a WHR more than 0.90 (n = 14) in comparison to those with a WHR less than 0.90 (n = 12, 2.47 +/- 0.29 v 1.66 +/- 0.18 pg/mL, respectively, P < .03). The corresponding plasma leptin level was significantly higher in obese women versus the control group (41.6 +/- 2.5 v22.3 +/- 2.9 ng/mL, P < .001) and was related to the BMI (r = .60, P < .01) but not to TNFalpha or the WHR. There were no significant differences in the corresponding IL-6 concentration between groups, and IL-6 did not correlate with TNFalpha, leptin, BMI, WHR, or insulin levels. In conclusion, circulating TNFalpha levels are higher in abdominal obesity compared with peripheral obesity, and may contribute to the insulin resistance that more commonly complicates the former pattern of fat distribution.

Hypothalamic Origin of the Metabolic Syndrome X

Abstract: The conspicuous similarities between Cushing's syndrome and the Metabolic Syndrome X open up the possibility that hypercortisolemia is involved also in the latter. Salivary cortisol is possible to measure during undisturbed conditions including perceived stressful events during everyday life. Such measurements clearly show that normally regulated cortisol secretion is associated with excellent health in anthropometric, metabolic, and hemodynamic variables. Upon perceived stress cortisol secretion is increased and followed by the Metabolic Syndrome X (insulin resistance, abdominal obesity, elevated lipids, and blood pressure). In a minor part of the population a defect, "burned-out" cortisol secretion, occurs with decreased sex steroid and growth hormone secretions, and strong, consistent associations with the Metabolic Syndrome X. Psychosocial and socioeconomic handicaps with tendencies to abuse and depressive-anxious mood changes are consistently associated. The feedback control of cortisol secretion by central glucocorticoid receptors (GR) is blunted, and the function of the GR is abnormal. This corresponds to a polymorphism early in the GR gene locus, which is also associated with abdominal obesity and insulin resistance and is found in 14% of the Swedish male population. We suggest that the Metabolic Syndrome X is due to a discretely elevated cortisol secretion, discoverable during reactions to perceived stress in everyday life. This is based on environmental factors and expressed with different impact depending on genetic susceptibility.

Infant and Child Growth and Fatness and Fat Distribution in Guatemalan Adults

Abstract: Being overweight especially in the abdominal region is a risk factor for cardiovascular disease the onset of diabetes in adults stroke and mortality. Malnutrition in utero or early childhood may lead to fatness later in life. The authors tested the hypothesis that poor linear growth during childhood predicts fatness and the high-risk fat patterning of young Guatemalan adults. Findings are based upon the analysis of prospectively collected data on 161 male and 372 female Guatemalans measured as children during 1969-77 and remeasured as adults in 1988-89 (men and women) and 1991-94 (women only). Childhood stunting was associated with a lower body mass index (BMI) and percent body fat in men while no association was found in women. Both male and female severely stunted children had significantly greater adult abdominal fatness after controlling for overall fatness and confounders. The adult waist:hip ratio was increased by 0.65 in men and 0.29 in women for each height-for-age z score less at age 3. Migration to urban centers was significantly associated with a greater waist:hip ratio in severely stunted females. In a subsample of 137 women short and thin newborns had significantly greater adult abdominal fatness compared with long and thin or short and fat newborns or children who became stunted postnatally. The adult waist/hip ratio was increased by 1.58 for each kilogram less birth weight. Findings suggest that in countries where maternal and child malnutrition exist in the context of rapid economic development and urban migration abdominal obesity and related chronic diseases are likely to increase.

Influence of Obesity and Body Fat Distribution on Postprandial Lipemia and Triglyceride-Rich Lipoproteins in Adult Women

Abstract: We know that upper body obesity is associated with metabolic complications, but we don't know how regional body fat distribution influences postprandial lipemia in obese adults. Thus, this study explored the respective effects of android or gynoid types of obesity and fasting triglyceridemia on postprandial lipid metabolism and especially triglyceride-rich lipoproteins. Twenty-four obese and 6 lean normotriglyceridemic women (control), age 24-57 yr, were enrolled. Among obese women with an android phenotype, 9 exhibited normal plasma triglyceride levels (mean: 1.38 mmol/L) (NTAO), and 7 displayed a frank hypertriglyceridemia (mean: 2.40 mmol/L) (HTAO). The 8 patients with a gynoid phenotype had normal triglyceride levels (mean: 1.00 mmol/L) (GO). All were given a mixed test meal providing 40 g triglycerides. Serum and incremental chylomicron triglycerides 0-7 h areas under the curve (AUCs) as well as triglyceride levels in apoB-48-containing triglyceride-rich lipoprotein (TRLs) or chylomicrons were significantly higher in HTAOs and NTAOs than in GOs and controls postprandially. The size of chylomicron particles was bigger in controls and GOs than in HTAOs and NTAOs postprandially. Android obese subjects showed abnormally elevated fasting apoB-48 and apoB-100 triglyceride-rich lipoprotein (TRL) levels. Most abnormalities that were found correlated to plasma levels of insulin and apoC-III. In conclusion, an abnormal postprandial lipid pattern is a trait of abdominal obesity even without fasting hypertriglyceridemia.

Psychosocial and socio-economic factors in women and their relationship to obesity and regional body fat distribution.

Abstract: BACKGROUND: Abdominal obesity, as well as psychosocial and socio-economic handicaps are risk factors for serious, prevalent diseases. Connections between these variables have been found in men. OBJECTIVE: The principal aim of the present study was to analyse the associations between psychosocial and socio-economic factors with body mass index (BMI) and the waist-to-hip circumference ratio (WHR) in women. DESIGN: A cohort study of data derived from questionnaires. SUBJECTS: 1137 women from a population sample of 1464 women born in 1956. MEASUREMENTS: Occupational, social and leisure time conditions, smoking and alcohol habits, as well as height, weight and waist and hip circumferences. RESULTS: BMI was associated with teetotalism and negatively to wine drinking. WHR correlated directly with cigarette smoking and negatively with consumption of wine and beer. Both BMI and WHR, adjusted for each other and for smoking and alcohol, showed independent associations with low education, unemployment and problems at work when employed, as well as with little physical activity and much TV-watching. In addition, the WHR showed a negative, independent relationship to housing conditions. CONCLUSION: These observations suggest psychosocial and socio-economic handicaps as well as a low physical activity in abdominally obese women. Similar observations have been made previously in men, but only with the WHR, suggesting an influence of obesity in these relationships in women only. Another interesting gender difference is the positive relationship between being married with BMI in men, as well as being divorced and living alone with the WHR in men only.

Insulin resistance: the fundamental trigger of type 2 diabetes.

Abstract: Type 2 diabetes is a heterogeneous condition that is not attributable to a single pathophysiological mechanism. In general, both insulin resistance and impaired insulin secretion are required for the disease to become manifest. Thus, as long as the pancreatic beta cells can compensate for the degree of insulin resistance, glucose tolerance remains normal. Clustering of type 2 diabetes in certain families and ethnic populations points to a strong genetic background for the disease. However, environmental factors such as obesity and a sedentary lifestyle are usually required to unmask the genes. Impaired insulin-stimulated glucose metabolism (particularly non-oxidative) in skeletal muscle represents a key feature of type 2 diabetes and is observed early in the pre-diabetic state. It is not clear, though, whether this represents an inherited defect in muscle or whether it develops secondarily, for example, to abdominal obesity. In favour of the latter hypothesis are findings that abdominal obesity and a low metabolic rate seem to precede the development of insulin resistance in offspring of type 2 diabetic patients. According to the thrifty gene hypothesis, individuals living in an environment with an unstable food supply could increase their probability of survival if they could maximize storage of surplus energy, for instance, as abdominal fat. Exposing this energy-storing genotype to the abundance of food typical of westernized societies is detrimental, causing insulin resistance and, subsequently, type 2 diabetes. There are a number of potential thrifty genes, including those that regulate lipolysis or code for the beta3-adrenergic receptor, the hormone-sensitive lipase, and lipoprotein lipase. Type 2 diabetes develops as a consequence of a collision between thrifty genes and a hostile affluent environment. Insulin resistance is a key trigger for the disease, and optimal management of type 2 diabetes should therefore aim to ameliorate insulin resistance early.

Abdominal obesity in the United States: prevalence and attributable risk of hypertension.

Abstract: Objective: The aim of this study was to determine the prevalence of abdominal obesity and its impact on the risks of hypertension in the US adult population. Design and methods: Data from the third US National Health and Nutrition Examination Surveys, 1988–1994, were utilised. Abdominal obesity was defined as waist circumference 102 cm in men and 88 cm in women. Hypertension was defined as mean diastolic blood pressure 90 mm Hg, systolic blood pressure 140 mm Hg or current treatment with prescribed hypertension medication. Prevalences of abdominal obesity were estimated in non-Hispanic White, non-Hispanic Black and Hispanic Americans. Gender-specific logistic regression analysis using empirical waist cut-off points was used to determine the risks of hypertension. The impact of abdominal adiposity on risk of hypertension was estimated from population-attributable risk adjusting for age, current smoking and alcohol intake. Results: The prevalences of abdominal obesity were 27.1%, 20.2% and 21.4% in White, Black and Hispanic men, respectively. The corresponding values in women were 43.2%, 56.0% and 55.4%. Abdominal obesity was found to be associated with a two to three-fold increased risk of hypertension in this population. In men, the attributable risk percent ranged from 20.9% in Hispanics to 27.3% in Whites and in women ranged from 36.5% in Whites to 56.5% in Hispanics. We estimated that 24 million adult men and 40 million adult women of Hispanic and non-Hispanic Black and White ethnicity were suffering from abdominal obesity. Conclusions: In this population, hypertension appears to be associated with abdominal obesity. The estimates of population attributable risks suggest that the risk of hypertension could be potentially reduced if waist size were reduced to <102 cm in men and <88 cm in women.

Neuroendocrine perturbations as a cause of insulin resistance

Abstract: Insulin resistance is followed by several prevalent diseases. The most common condition with insulin resistance is obesity, particularly when localized to abdominal, visceral regions. A summary of recent reviews on the pathogenesis of systemic insulin resistance indicates that major factors are decreased insulin effects on muscular glycogen synthase or preceding steps in the insulin signalling cascade, on endogenous glucose production and on circulating free fatty acids (FFA) from adipose tissue lipolysis. Contributions of morphologic changes in muscle and other factors are considered more uncertain. Newly developed methodology has made it possible to determine more precisely the neuroendocrine abnormalities in abdominal obesity including increased cortisol and adrenal androgen secretions. This is probably due to a hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, amplified by inefficient feedback inhibition by central glucocorticoid receptors, associated with molecular genetic defects. Secondly, secretion of gender-specific sex steroid hormones becomes inhibited and the sympathetic nervous system activated. At this stage the HPA axis shows signs of a 'burned-out' condition, and cortisol secretion is no longer elevated. Cortisol counteracts the insulin activation of glycogen synthase in muscle, the insulin inhibition of hepatic glucose production and the insulin inhibition of lipolysis in adipose tissue, leading to the well-established systemic insulin resistance caused by excess cortisol. This is exaggerated by increased free fatty acid mobilization, particularly with a concomitant elevation of the activity of the sympathetic nervous system. Furthermore, capillarization and fiber composition in muscle are changed. These are the identical perturbations responsible for insulin resistance in recent reviews. The diminished sex steroid secretion in abdominal obesity has the same consequences. It is thus clear that insulin resistance may be induced by neuroendocrine abnormalities, such as those seen in abdominal obesity. These endocrine perturbations also direct excess fat to visceral fat depots via mechanisms that are largely known, indicating why abdominal obesity is commonly associated with insulin resistance. This possible background to the most prevalent condition of insulin resistance has been revealed by development of methodology that allows sufficiently sensitive measurements of HPA axis activity. These findings demonstrate the power of neuroendocrine regulations for somatic health.

Relationship of internalized racism to abdominal obesity and blood pressure in Afro-Caribbean women.

Abstract: Racism is associated with increased psychosocial stress and blood pressure in blacks. However, little is known of the relationship of racism to other features of insulin resistance syndrome. This study examined the relationship of internalized racism to abdominal obesity and elevated blood pressure in a population of black Caribbean women aged 20-55 years. One hundred thirty-three randomly selected women from the island of Barbados comprised the study sample. Data collected included anthropometric and blood pressure measurements, and information about internalized racism, anxiety, and depression. The stress measures including anxiety, depression, and internalized racism were significantly correlated with waist circumference (r = .25, r = .21, and r = .25). After adjusting for age, education, anxiety, and depression, internalized racism remained significantly correlated with waist circumference. The odds ratio associated with development of abdominal obesity among those with high internalized racism (OR = 2.4 [95% CI, 1.1,5.3]) was significant (P < .05) after adjusting for age, education, and body mass index. Blood pressure was not independently related to internalized racism. Studies comparing black-white differences in diseases for which abdominal obesity is a risk factor (eg, diabetes and cardiovascular disease) should take into account the potential role of internalized racism in defining the differences between ethnic groups.

Growth hormone and the metabolic syndrome.

Abstract: The association of several risk factors, obesity, dyslipoproteinemia, hepatic steatosis, insulin resistance and hypertension with Type 2 (non-insulin-dependent) diabetes mellitus and myocardial infarction has long been known and has been termed the "metabolic syndrome". In 1988 Reaven introduced syndrome X as the link between insulin resistance and hypertension. It has been suggested that a critical factor in the association between obesity, Type 2 diabetes and cardiovascular morbidity is the mass of intraabdominal fat. Striking similarities exist between the metabolic syndrome and untreated growth hormone (GH) deficiency in adults. The central findings in both these syndromes are abdominal/visceral obesity and insulin resistance. Other features common to both conditions are premature atherosclerosis and increased mortality from cardiovascular diseases. These similarities indicate that undetectable and low levels of GH may be of importance in the metabolic aberrations observed in both these conditions. Recent investigations have found that abdominal/visceral distribution of adipose tissue is associated with endocrine disturbances including increased activity of the hypothalamic-pituitary-adrenal axis and a blunted secretion of GH and sex steroids. Theoretically, these endocrine perturbations can be a consequence of obesity, but the endocrine aberrations may have causal effects. We studied moderately obese, middle-aged men with a preponderance of abdominal body fat. As a group, they had slight to moderate metabolic changes known to be associated with abdominal/visceral obesity. Nine months of GH treatment reduced their total body fat and resulted in a specific and a marked decrease in both abdominal subcutaneous and visceral adipose tissue. Moreover, insulin sensitivity improved and serum concentrations of total cholesterol and triglyceride decreased. Diastolic blood pressure also decreased. The finding that GH replacement in men with abdominal obesity can diminish the negative metabolic consequences of visceral obesity suggests that low levels of this hormone are of importance for the metabolic aberrations associated with visceral/abdominal obesity.

Low serum insulin in traditional pacific islanders—The Kitava study

Abstract: Increased serum insulin is related to abdominal obesity and high blood pressure in affluent societies where insulin, weight, and blood pressure typically increase with age. The increased insulin level has been thought to reflect insulin resistance, a well-known associated factor in the metabolic syndrome. In most nonwesternized populations, body weight and blood pressure do not increase with age and abdominal obesity is absent. However, it is not known whether serum insulin likewise does not increase with age in nonwesternized societies. Fasting levels of serum insulin were measured cross-sectionally in 164 subsistence horticulturalists aged 20 to 86 years in the tropical island of Kitava, Trobriand Islands, Papua New Guinea, and in 472 randomly selected Swedish controls aged 25 to 74 years from the Northern Sweden WHO Monitoring Trends and Determinants in Cardiovascular Diseases (MONICA) Study. In Kitava, the intake of Western food is negligible and stroke and ischemic heart disease are absent or rare. The body mass index (BMI) and diastolic blood pressure are low in Kitavans. The main outcome measures in this study were the means, distributions, and age relations of serum insulin in males and females of the two populations. Serum fasting insulin levels were lower in Kitava than in Sweden for all ages (P < .001). For example, the mean insulin concentration in 50- to 74-year-old Kitavans was only 50% of that in Swedish subjects. Furthermore, serum insulin decreased with age in Kitava, while it increased in Sweden in subjects over 50 years of age. Moreover, the age, BMI, and, in females, waist circumference predicted Kitavan insulin levels at age 50 to 74 years remarkably well when applied to multiple linear regression equations defined to predict the levels in Sweden. The low serum insulin that decreases with age in Kitavans adds to the evidence that a Western lifestyle is a primary cause of insulin resistance. Low serum insulin may partly explain the low prevalence of cardiovascular disease in Kitavans and probably relates to their marked leanness.

A comparison of proxy measures of abdominal obesity in Chinese, European and South Asian adults.

Abstract: Summary Aims To assess whether four proxy measures of abdominal obesity (waist circumference; waist-to-hip ratio (WHR); waist-to-height ratio and C index, a measure of body shape) were uniformly associated with features of the metabolic syndrome (triglycerides, high density lipoprotein (HDL) cholesterol, 2-h glucose) in three ethnic groups. Methods Anthropometric and biochemical data were collected in 629 Europeans (320 men, 309 women), 380 Chinese (183 men, 197 women) and 597 South Asians (275 men, 322 women) aged 25–64 years in Newcastle upon Tyne, UK. Linear regression models were used to determine whether relationships differed between ethnic groups. Results Linear regression analysis showed that most proxy measures of abdominal obesity were associated with features of the metabolic syndrome. There were significant interactions between WHR and ethnicity and C index and ethnicity in the relationship with log triglycerides when comparing European and Chinese women. Interactions existed between all proxy measures and ethnicity in the relationship with log triglycerides and HDL cholesterol when comparing European and South Asian women. In men, interactions between ethnicity and waist circumference, WHR and C index when comparing Europeans and South Asians, and between ethnicity and WHR and C index when comparing South Asian and Chinese for log 2-h glucose were significant (P < 0.001). All interactions remained significant when differences in smoking, alcohol and physical activity were taken into account. Conclusions Not all the proxy measures of abdominal obesity were consistently related to features of the metabolic syndrome across the ethnic groups studied. However, waist circumference and waist to height ratio were the most consistent and WHR the least when comparing across the ethnic groups.

Physical activity, obesity and blood lipids.

Abstract: PURPOSE: To present the evidence concerning the influence of physical activity on the dyslipidaemia of obesity and overweight. METHODS: Review of a personal library of literature on the interactions of physical activity, lipoprotein metabolism and body fatness. SUMMARY OF FINDINGS: Obesity, in particular abdominal obesity, is associated with dyslipidaemia—specifically elevated plasma concentrations of triacylglycerol (TAG) in the fasted state, an exaggerated postprandial rise in plasma TAG, low concentrations of high density lipoprotein cholesterol (HDL) and possibly a preponderance of small dense low density lipoproteins. Regular physical activity contributes to the avoidance of overweight and hence to the development of dyslipidaemia. Although low levels of body fatness contribute to the high levels of HDL cholesterol and the low levels of TAG in trained people there are other important determinants of these characteristics. In particular, exercise (and probably training, that is regular, frequent exercise over months and years) enhances the metabolic capacity for TAG, possibly through mechanisms involving increased activity of lipoprotein lipase. This, in turn, has effects on other lipoprotein species such that the transport of TAG and cholesterol in the circulation is improved. There is evidence for a dose–response relationship, with for example, higher levels of HDL cholesterol in men and women who expend more energy in exercise. For the majority of healthy, sedentary adults frequent, moderate intensity exercise equivalent to a total gross energy expenditure of about 8.5 MJ per week is probably a sufficient to influence lipoprotein lipids.

Sex hormone-binding globulin levels in middle-aged premenopausal women. Associations with visceral obesity and metabolic profile.

Abstract: OBJECTIVE: Low sex hormone-binding globulin (SHBG) levels in women are associated not only with hyperinsulinemia, increased risk for cardiovascular disease, and type 2 diabetes but also with excess body fatness and abdominal obesity. We tested the hypothesis that an elevated total or intra-abdominal adipose tissue accumulation mediates the relationship between low SHBG levels and an altered metabolic profile. RESEARCH DESIGN AND METHODS: We measured body composition (dual-energy X-ray absorptiometry [DEXA]) and body fat distribution (computed tomography) in 52 middle-aged (46.7 +/- 0.4, mean +/- SEM) premenopausal women. Insulin and glucose responses to a 75-g oral glucose load and plasma lipid-lipoprotein levels were also measured. RESULTS: Low plasma SHBG concentrations were associated with increased total body fat mass (r = -0.41, P < 0.005) and subcutaneous abdominal (r = -0.39, P < 0.005) and intra-abdominal (r = -0.37, P < 0.008) adipose tissue area. Low SHBG was also associated with a greater insulin response to oral glucose (r = -0.40, P < 0.005), higher triglyceride levels (r = -0.29, P < 0.05), higher cholesterol/HDL cholesterol ratio (r = -0.51, P < 0.005), but lower HDL cholesterol concentrations (r = 0.65, P < 0.005). When matched for intra-abdominal fat or total fat mass, subjects with either low or high SHBG showed no difference in the insulin response to an oral glucose challenge. Statistical adjustment for differences in intra-abdominal adipose tissue accumulation or total body fat mass also eliminated the associations between SHBG levels and metabolic variables, with the exception of the association between SHBG and HDL cholesterol levels (r = 0.52, P < 0.005). CONCLUSIONS: Our results suggest that the previously reported relationship between low SHBG levels and increased metabolic disease risk in women is mediated, to a large extent, by concomitant variation in body fatness and intra-abdominal adipose tissue accumulation.

Is abdominal fat preferentially reduced in response to exercise-induced weight loss?

Abstract: Purpose: It is known that a preferential deposition of fat in the abdominal region is the obesity phenotype that conveys the greatest health risk. Although physical activity is commonly prescribed to reduce obesity, the influence of exercise-induced weight loss on abdominal fat is unclear. This review was undertaken to clarify whether abdominal fat is preferentially reduced consequent to weight loss induced by regular exercise. Methods: A literature search (Medline, 1966-1998) was performed using appropriate keywords to identify studies reporting changes in both whole body and abdominal fat in response to exercise. Results: At present there are no randomized controlled trails (RCT) wherein it was clear that exercise alone induced weight loss. For the four RCT within which regular exercise was not associated with weight loss, abdominal fat measured by waist circumference was unchanged. A similar trend is observed for the nonrandomized studies. Abdominal obesity as measured by waist circumference is unchanged for those studies reporting no loss in weight or fat; however, a modest reduction (∼3 cm) is observed in response to exercise-induced weight loss of about 3 kg. Without exception, these studies were not designed to determine whether abdominal obesity was preferentially reduced. Absent from the literature are RCT that employ imaging techniques (e.g., computerized tomography or magnetic resonance imaging) to determine whether exercise-induced weight loss is associated with reductions in either visceral or abdominal subcutaneous fat. However, the findings from four nonrandomized or controlled studies report that exercise with or without weight loss is associated with reductions in both visceral and subcutaneous fat. Conclusions: There is insufficient evidence to determine whether exercise-induced weight loss is associated with reductions in abdominal fat. Clearly there is a need for carefully controlled studies wherein the primary aim is to determine the influence of regular exercise on total and abdominal adiposity.

Correction of hyperandrogenemia by laparoscopic ovarian cautery in women with polycystic ovarian syndrome is not accompanied by improved insulin sensitivity or lipid-lipoprotein levels

Abstract: Polycystic ovarian syndrome (PCOS) is a common disorder associated with hyperandrogenemia and infertility. Abdominal obesity, insulin resistance, and dyslipoproteinemias are other common metabolic disorders typically found in women with PCOS. The cause-effect relationship between hyperandrogenemia and insulin resistance-dyslipoproteinemia remains unclear. In this study, we have investigated the changes in androgenemia, insulin sensitivity, and plasma lipid-lipoprotein levels after laparoscopic ovarian cautery (LOC) for ovulation induction in eight infertile women with clomiphene citrate-resistant PCOS. After LOC, significant decreases in androstenedione (43%), testosterone (48%), and free testosterone (48%) concentrations were observed (P < 0.05). Glucose utilization during an euglycemic-hyperinsulinemic clamp did not change after LOC. In addition, no significant changes after the surgical procedure were observed for cholesterol, triglycerides, and apolipoprotein concentrations measured in total plasma and in different lipoprotein fractions. In conclusion, within the short duration of observation of this study, our findings demonstrate that insulin resistance and lipoprotein abnormalities associated with PCOS are not secondary to hyperandrogenemia. The clinician, therefore, must be cognizant of the persistence of these metabolic risk factors for cardiovascular disease once successful ovulation and fertility is restored, and institute appropriate monitoring, counseling, and medical intervention as required.

Effect of obesity and insulin resistance on resting and glucose-induced thermogenesis in man.

Abstract: OBJECTIVE: to assess the impact of obesity and insulin sensitivity on resting (REE) and glucose-induced thermo-genesis (GIT) DESIGN: Data from 322 studies carried out in non-diabetic subjects of either gender, covering a wide range of age (18–80 y) and body mass index (BMI, 18–50 kg/m2) MEASUREMENTS: Insulin sensitivity and thermogenesis were measured by combining the euglycaemic insulin clamp technique with indirect calorimetry RESULTS: REE was inversely related to age (P=0001) and the respiratory quotient (P=003), and positively related to BMI, lean body mass (LBM), fat mass, and percentage fat mass (all P<00001) In a multiple regression model, LBM-adjusted REE was estimated to decline by 9% between 18 and 80 y, independently of obesity and insulin sensitivity In contrast, GIT was strongly associated with insulin sensitivity (P<00001) but not with gender, age or BMI By multiple regression analysis, GIT was linearly related to insulin sensitivity after controlling for gender, age, BMI and steady-state plasma insulin levels Furthermore, both of the main components of insulin-mediated glucose disposal (glucose oxidation and glycogen synthesis) correlated with GIT independently of one another In the subset of subjects (n=89) in whom waist-to-hip ratio (WHR) measurements were available, GIT was inversely associated with WHR (P<0001 after adjustment by gender, age, BMI, insulin sensitivity and steady-state plasma insulin concentration) In this model, a significant interaction between WHR and gender indicated a stronger adverse effect on GIT of a high WHR in women than in men CONCLUSIONS: In healthy humans, age, lean mass and respiratory quotient are the main independent determinants of resting thermogenesis In contrast, insulin sensitivity and, to a lesser extent, abdominal obesity are the principal factors controlling glucose-induced thermogenesis

Contribution of the cholesteryl ester transfer protein gene TaqIB polymorphism to the reduced plasma HDL-cholesterol levels found in abdominal obese men with the features of the insulin resistance syndrome.

Abstract: Contribution of the cholesteryl ester transfer protein gene TaqIB polymorphism to the reduced plasma HDL-cholesterol levels found in abdominal obese men with the features of the insulin resistance syndrome

Obesity-related phenotypes and the beta3-adrenoceptor gene variant in postmenopausal women.

Abstract: We examined the hypothesis that postmenopausal women with the beta3-adrenoceptor gene variant (Trp64Arg) have reduced total daily energy expenditure (TEE), altered free fatty acid kinetics, and increased intra-abdominal fat. A secondary objective was to examine whether the obese state masks the effect of the variant on resting metabolic rate (RMR). There were 23 obese heterozygous women with the genetic variant (age 58 +/- 6 years; BMI 36 +/- 7 kg/m2) who were compared with 19 homozygous obese women with the normal allele (age 56 +/- 4 years; BMI 36 +/- 3 kg/m2). Daily energy expenditure was determined from doubly labeled water and indirect calorimetry, lipolysis from infusion of [1-13C]palmitate, and body fat distribution from computed tomography. No significant differences were found in TEE, RMR, energy expenditure of physical activity, the thermic effect of a meal, fat oxidation as estimated by fasting and postprandial respiratory quotients (RQs), or rate of lipolysis. Similarly, no difference was found in visceral adipose tissue and abdominal subcutaneous fat areas. When RMR was compared between obese (n = 23) and never-obese women with the Trp64Arg variant (n = 16), we found a 317 kcal/day lower RMR in never-obese women after controlling for fat mass, fat-free mass, and age (P < 0.0017). These results do not support the hypothesis that already obese women with the Trp64Arg polymorphism of the beta3-adrenergic receptor gene have lower daily energy expenditure, altered lipolysis, and increased abdominal obesity. On the other hand, the lower RMR in never-obese women suggests that the obese state may mask a moderate effect of the Trp64Arg variant on energy expenditure. Although these results need to be confirmed in other populations, the obese state may have been a confounding factor in previous studies of the beta3-adrenoceptor Trp64Arg variant and energy expenditure.

Insulin resistance syndrome: options for treatment.

Abstract: Background.Insulin resistance is characterized by impaired responsiveness to endogenous or exogenous insulin. Loss of responsiveness is associated with a “clustering” of cardiovascular risk factors that includes abdominal obesity, hypertension, dyslipidemia, glucose intolerance, and hyperins

The influence of abdominal obesity and chronic work stress on ambulatory blood pressure in men and women.

Abstract: OBJECTIVE: To assess the influence of abdominal obesity and work stress (operationalised as low control over work) on ambulatory blood pressure on a working day and evening. PARTICIPANTS AND METHODS: 156 school teachers (58 men and 98 women) carried out ambulatory blood pressure and heart rate monitoring on a work day and evening. Cardiovascular activity was also measured under baseline conditions on another occasion, when body weight, height, waist and hip circumference were assessed. Perceived control over work was assessed by questionnaire, along with mental health, anger expression and social support. 126 participants repeated the protocol after 12 months. Waist/hip ratio was used as the index of abdominal obesity. RESULTS: Baseline blood pressure was positively associated with waist/hip ratio in men, but ambulatory blood pressure and heart rate were not independently related to waist/hip ratio or job control. However, blood pressure and heart rate recorded during the working day and evening were elevated in men with high waist/hip ratio who experienced low job control, independently of age and body weight. Effects for diastolic blood pressure and heart rate were replicated after 12 months. Body mass index was not related to blood pressure or heart rate during the day or evening after adjustment for age and waist circumference. Low job control was associated with poor psychological well-being, negative mood and lack of social support. CONCLUSIONS: The results are consistent with the hypothesis that abdominal obesity in men is characterised by a tendency towards heightened stress-induced physiological activation, but that this tendency will only be manifest in the presence of appropriate environmental challenges such as chronic work stress.

Abdominal adiposity in six populations of West African descent: prevalence and population attributable fraction of hypertension.

Abstract: OKOSUN, IKE S., TERRENCE E. FORRESTER, CHARLES N. ROTIMI, BABATUNDE O. OSOTIMEHIN, WALINJOM F. MUNA, AND RICHARD S. COOPER. Abdominal adiposity in six populations of West African descent: prevalence and population attributable fraction of hypertension. Obes Res. Objectives: The objective of this investigation was to examine the prevalence of abdominal adiposity and its association with the prevalence of hypertension among African descent populations in Nigeria, Cameroon, Jamaica, St. Lucia, Barbados, and the United States (US). Research Method: The data for this investigation were obtained from the International Collaborative Study on Hypertension in Blacks. Hypertension was defined as mean diastolic blood pressure ≥90 mmHg, systolic blood pressure ≥140 mmHg or current treatment with prescribed anti-hypertension medication. Abdominal overweight was defined as waist circumference (WC) ≥94 and ≥80 cm for men and women, respectively. Abdominal obesity was defined as WC ≥102 and ≥88 cm for men and women, respectively. We estimated the site-specific prevalence of abdominal overweight and obesity across age and body mass index cut-points. We also calculated the population attributable fraction (AF) of hypertension due to abdominal adiposity. Results: The prevalence of hypertension in these populations was tightly linked to abdominal adiposity. Increases in abdominal overweight accompanied an increasing degree of Westernization, rising from 6. 4% and 26. 3% in Nigeria, 16. 5% and 62. 8% in Cameroon, 15. 8% and 58. 6% in Jamaica, 14. 3% and 62. 1% in St. Lucia, 21. 4% and 70. 3% in Barbados to 38. 9%, and 76. 4% in the US for men and women, respectively. The corresponding values for abdominal obesity were 1. 6% and 12. 3% in Nigeria, 5. 1% and 38. 9% in Cameroon, 5. 5% and 34. 0% in Jamaica, 2. 7% and 40. 7% in St. Lucia, 7. 8% and 44. 7% in Barbados to 21. 7% and 54. 1% in the US for men and women, respectively. Body mass index-adjusted estimates of AF suggest that in most of these populations, especially in females, avoidance of abdominal overweight or obesity would help to curb the development of hypertension. Discussion: An important public health challenge is to clarify how lifestyle factors influence risks of abdominal adiposity and ultimately the increased risk of cardiovascular diseases.

Abdominal obesity increases overnight cortisol excretion.

Abstract: Although plasma and 24 h urinary free cortisol (UFC) levels are normal in obese subjects, pharmacological investigations have identified minor hypothalamo-pituitary-adrenal axis differences in patients with abdominal body fat distribution (A-BFD) vs peripheral BFD (P-BFD). Using recent tools such as saliva cortisol or overnight urinary free cortisol upon creatinine ratio (UFC/UC) determinations, we have investigated a population of obese females according to their body fat distribution. In-patients subjects (no.=82) were subjected to routine biochemical testing, 24 h and overnight UFC/UC, basal and post-1mg overnight dexamethasone-suppressing test plasma and saliva cortisol determinations. Central obesity defined by a waist-to-hip ratio (WHR) >0.85 was found in 64% of the subjects vs 87% when defined by waist girth (WG) corrected for age. Despite identical body mass index, A-BFD subjects were more prone to hypertension using both classifications and had higher triglycerides (WHR classification) or higher triglycerides, cholesterol and glycemia (WG classification). Plasma cortisol levels were similar but saliva cortisol levels were lower in the A-BFD group using the WG classification. The 24 h UFC/UC were similar but the overnight UFC/UC were higher in the A-BFD group using the WHR classification. These mild differences in cortisol nocturnal secretion and free cortisol indexes in subjects with different body fat mass distribution suggest that their hypothalamo-pituitaryadrenal axis has a spontaneously subtly different regulation.

Lipoprotein alterations, abdominal fat distribution and breast cancer

Abstract: SUMMARY Plasma lipid profile and abdominal obesity have been associated with breast cancer risk, however published resuits'have been inconsistent. To clarify these associations we studied lipid and lipoprotein alterations, obesity degree and body fat distribution, in 30 newly diagnosed breast cancer patients without treatment and 30 controls matched by age and menopausal status. Both pre and postmenopausal breast cancer patients presented higher body mass index, waist/hip ratio and insulin levels than their matched controls. An increase in triglycerides and a decrease in HDL-cholesterol, especially in the HDLz subfraction, were observed in patients with breast cancer. Besides, HDL particle from these patients showed increased apo AJHDL-cholesterol ratio. These alterations were correlated with waist/hip ratio. The association between lipoprotein alterations and abdominal obesity independent of menopausal status, in untreated newly diagnosed breast cancer patients is reported for the first time in this study.