The relative contribution of body fat and fat pattern to blood pressure level

The association of waist-hip ratio and risk factors for development of IDDM complications in an IDDM adult population

The role of waist-to-hip ratio (WHR) in the metabolic disturbance of IDDM has not been widely explored. Cross-sectional data from the Epidemiology of Diabetes Complications Study were used to examine the associations between WHR and risk factors for IDDM complications such as lipid or lipoprotein levels, blood pressure and fibrinogen. A total of 586 adults (greater than or equal to 18 years of age) were examined. WHR was calculated as the mean of duplicate waist circumference measurements made at mid-point between the iliac crest and the lower costal margin in mid-axillary line divided by the mean of duplicate maximum hip measures. WHR was positively correlated with total cholesterol, LDL-cholesterol, triglycerides, systolic and diastolic blood pressure and fibrinogen univariately for both sexes. WHR was negatively correlated with HDL-cholesterol. These correlations remained significant after adjustment for age among females and became less strong, although still significant, for males. The independent effects of WHR to these IDDM risk factors, assessed by multiple linear regression, indicated WHR was related to adverse lipid and lipoprotein levels, but not to fibrinogen or blood pressure. These findings underscore the importance of targeting intervention to IDDM individuals who have a high WHR to reduce known risk factors for IDDM complications especially those for cardiovascular disease, and is consistent with the hypothesis that insulin resistance may have a role to play in IDDM complications.

Sex-dependence of body fat distribution in patients with obesity and hypertension

The relationship of body fat distribution with blood pressure, fat cell weight and extracellular fluid volume was studied and compared in 20 obese hypertensive men and 20 obese hypertensive women of similar age, degree of overweight and blood pressure level. Body fat distribution, as reflected by the ratio between waist and hip circumference (W/H ratio), was significantly higher in male than in female obese patients. The W/H ratio was positively and independently correlated with systolic arterial pressure both in males and females. However, for the same W/H ratio, systolic arterial pressure was higher in females. The W/H ratio was positively correlated with gluteal fat cell weight only in males and not in females. Both in males and females, the W/H ratio was positively correlated with extracellular fluid volume, independently of the level of blood pressure level and/or the degree of obesity. The study provided evidence that the relationship between body weight and blood pressure in obese hypertensives is affected by the sex-dependence of body fat distribution with possible interferences on fat cell weight and extracellular fluid volume. Several epidemiological studies have emphasized the positive correlation observed between body weight and blood pressure in many. Many investigations have documented the association of blood pressure with body weight, weight to height, overweight or other indices of fatness such as skinfold thickness. However, the correlation coefficients of these different relationships were found constantly small, indicating that the relationship between overweight and blood pressure is somewhat complex. In patients with hypertension, body weight was shown to be strongly related with the levels of both blood pressure and extracellular fluid volume. On the other hand, patients with overweight and hypertension were found to be principally affected by hypertrophic obesity, as shown by the evaluation of fat cell weight. However these findings were exclusively observed in males. No solid data were reported in females. The relationships between body weight and extracellular fluid on one hand, and between body weight and fat cell weight on the other hand, are certainly different in males and in females. First, in females, extracellular fluid volume is submitted to cyclic changes in sodium balance involving the effect of sex steroid hormones. Second, body fat distribution, a parameter which is weakly correlated to blood pressure, is different in males and females. In males, body fat predominates in the upper part of the body while, in females, adiposity is mainly observed in the lower part of the body.(ABSTRACT TRUNCATED AT 400 WORDS)

Postmenopausal hormone replacement therapy prevents central distribution of body fat after menopause

The reduction in cardiovascular risk induced by hormone replacement therapy is only partly explained by changes in serum lipids and lipoproteins. As body composition and body fat distribution in particular are independent predictors of cardiovascular disease, we investigated the effect of postmenopausal hormone therapy on body composition parameters directly measured. Sixty-two early postmenopausal women were followed up for 2 years in a prospective, randomized, placebo-controlled study. We found that combined estrogen-progestogen therapy prevented the increase in abdominal fat after menopause (P less than .05), and that this effect was independent of the effect on serum lipids and lipoproteins. The therapy reduced postmenopausal bone loss significantly (P less than .001), whereas it did not have a statistically significant influence on total body fat mass or total lean body mass. The findings of the present study suggest that some of the protective impact of postmenopausal hormone therapy on cardiovascular disease may be explained by the effect on body composition, in particular abdominal fat.

Validation of body composition by dual energy X-ray absorptiometry (DEXA)

The present study validates the use of dual energy X-ray absorptiometry (DEXA) for measurement of body composition. The precision error was expressed as the SD (CV%) for fat mass, FAT%, lean tissue mass, and total body bone mineral: 1.1 kg (6.4%), 1.6% (5.7%), 1.4 kg (3.1%), and 0.03 kg (1.2%), respectively. The accuracy study in vitro used (1) mixtures of water and alcohol, (2) mixtures of ox muscle and lard, and (3) dried bones. In the clinically relevant range of values there were only small influences on DEXA measurements of variations in amount and composition of the soft tissue equivalents. The accuracy study in vivo compared the components of body composition measured recently by DEXA and earlier by dual photon absorptiometry, counting of naturally occurring total body 40K, and body density by underwater weighing in 25 healthy adult subjects. We found agreement between fat percentage (and lean body mass) by DEXA and the three established measurements modalities; mean differences were (-5.3 to -0.4%) and (-0.7 to 2.5 kg) for fat percentage and lean body mass, respectively. We conclude that DEXA provides a new method of measuring body composition with precision and accuracy errors, which are compatible with the application of DEXA in group research studies and probably also in clinical measurements of the single subject.

Obesity, blood pressure, and the sympathetic nervous system

Obesity has long been recognized as a major risk factor for the development of hypertension. Recently, insulin level has been shown to correlate with blood pressure in clinical and population-based studies. Since insulin is a major signal in the relationship between dietary intake and sympathetic nervous system activity, the possibility that insulin-mediated sympathetic stimulation is involved in the pathogenesis of hypertension in the obese has been raised. This hypothesis, developed on the basis of studies in laboratory rodents and normal human subjects, is currently being tested in the Normative Aging Study in Boston. Utilizing epidemiologic techniques applied to this defined population, evidence in support of this hypothesis has been accumulated. The preliminary results indicate that in this population, the abdominal form of obesity is associated with higher insulin levels and increased 24-hour urinary norepinephrine excretion (an index of sympathetic activity).

Skinfold and body circumferences as measures of body fat patterning in a French female active population: relationships with the metabolic risk profile

Body mass index (BMI), various anthropometric indices of abdominal fat distribution and some metabolic variables (blood lipids, fasting glucose, blood pressure) were measured in 408 French-born women from an occupational population who volunteered for the study. The aim of the study was to determine the best index for describing the relationships between the body fat pattern and the metabolic risk profile. The four age-adjusted circumference ratios (waist/hip, waist/thigh, xiphoid/hip, xiphoid/thigh) showed similar associations with the metabolic variables whereas the three age-adjusted skinfold ratios (epigastric/thigh, mesogastric/thigh, hypogastric/thigh) tended to be more weakly associated with the metabolic variables, particularly with apolipoprotein (Apo) B and fasting glucose. Multiple regression analyses showed that age-adjusted BMI was significantly related to high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, Apo A and Apo B, and blood pressure, independently of abdominal fat distribution. After controlling for the effects of BMI, the waist/thigh ratio remained significantly associated to triglyceride, Apo B, fasting glucose, and systolic blood pressure, whereas the waist/hip ratio and the mesogastric/thigh skinfold ratio were significantly related only to triglyceride and systolic blood pressure independently of BMI. With the exception of triglyceride and fasting glucose, the degree of association between the metabolic variables and the abdominal fat distribution tended to be weaker than that observed with the BMI. These results emphasize the importance of the global corpulence in the levels of metabolic variables. However, all indices of abdominal fat distribution were, to varying degrees, independently associated with an unfavorable metabolic profile. Among them, the waist/thigh circumference ratio seems to be a useful indicator of the body fat pattern in women.

The association of body fat location with haemodynamic and metabolic status in men and women aged 21-60 years

The importance of body fat location as a predictor of metabolic aberrations was evaluated in 214 males and 244 females [aged 21-60] randomly selected from the patients of one general practice of Castel D'Azzano (Italy). The metabolic pattern, indexed by blood pressure, blood glucose, uric acid, serum triglycerides, HDL- and LDL-cholesterol was summarized in a haemodynamic-metabolic score (HMS). Association of HMS with age, anthropometric variables (skinfold thicknesses, girth lengths) and degree of overweight (body mass index, BMI) was evaluated in males and females using multiple regression analysis. Body fat location was associated with metabolic status independent of age in both sexes. This association was also independent of the degree of overweight. BMI, in general, was associated with HMS to a greater extent than anthropometric variables, except for waist girth; when its effect was taken into account BMI did not significantly improve the prediction power of HMS values in males. Among skinfolds, epimesogastric showed in both sexes the highest association with HMS. These results support the abdominal adiposity hypothesis and suggest that waist circumference could be a good index for assessing metabolic status. The abdominal location of adipose tissue, more than just the degree of overweight, could play a role in obesity related disorders.

Body fat distribution in men with angiographically confirmed coronary artery disease

Body fat distribution and its relationship to coronary artery disease and established cardiovascular risk factors have been studied in a cohort of 286 men aged between 30 and 74 years undergoing coronary angiography. 207 (72.4%) patients showed stenosis (greater than 30%) or occlusion of one or more coronary arteries. whereas the remaining 79 (27.6%) men were free of coronary lesions and served as a control group. 112 men with angiographically defined coronary artery disease had an additional history of myocardial infarction. Body fat distribution was assessed by determining the waist-to-hip circumference ratio. A stepwise logistic regression analysis revealed that in addition to LDL-cholesterol (P = 0.0001) and age (P = 0.0005) an abdominal type of body fat distribution (P = 0.0129) is also a significant risk indicator for the occurrence of coronary artery disease (CAD) independent of body weight and other factors such as total cholesterol, HDL-cholesterol, triglycerides, insulin, systolic and diastolic blood pressure. The results of this study suggest that an abdominal type of fat distribution is associated with an increased risk of coronary artery disease.

Behavioral covariates of waist-to-hip ratio in Rancho Bernardo

We examined lifestyle and dietary habits in 685 men and 943 women (mean age 67 years) who completed an interview, examination, and food frequency questionnaire in 1984-87. Waist-to-hip ratio increased with age and body mass index in both men and women. In multiple regression, waist-to-hip ratio was independently associated with smoking, alcohol consumption, and exercise in men, and with smoking and alcohol consumption in women. The data suggest that waist-to-hip ratio is affected, at least in part, by behavioral, and potentially modifiable, factors.

Close correlation of intra-abdominal fat accumulation to hypertension in obese women

The relation between intra-abdominal visceral fat accumulation and blood pressure was investigated in 67 obese women (mean body mass index, 33.6 +/- 3.1; average age, 50 +/- 11 years). As an index of intra-abdominal fat accumulation, the ratio of the intra-abdominal visceral fat area to subcutaneous fat area was determined using a computed tomographic section at the level of the umbilicus. When the obese subjects were divided into a hypertensive group and a normotensive group, the ratio of the intra-abdominal visceral fat area to subcutaneous fat area in the hypertensive group was significantly higher (0.53 +/- 0.33 versus 0.29 +/- 0.12, p less than 0.01). Significant correlations between the ratio of intra-abdominal visceral fat area to subcutaneous fat area and systolic blood pressure (r = 0.62, p less than 0.001) and diastolic blood pressure (r = 0.53, p less than 0.001) also were found. However, no significant difference existed in either the body mass index or the waist-to-hip circumference ratio between the hypertensive and normotensive groups. Plasma renin activity, aldosterone, epinephrine, and norepinephrine levels were not significantly different between the two groups. Moreover, the correlation between the ratio of the intra-abdominal visceral fat area to subcutaneous fat area ratio and blood pressure was found independent of age and body mass index by multiple regression analyses. We conclude that intra-abdominal fat accumulation itself may play an important role in the pathogenesis of hypertension in obesity.

Body fat distribution, blood pressure, and hypertension. A prospective cohort study of men in the normative aging study

The relation between the abdominal accumulation of body fat, blood pressure, and hypertension was assessed prospectively among 1972 male participants in the Veterans Administration Normative Aging Study. Body mass index (BMI = weight [kg]/height [m]2) and the ratio of abdominal circumference to hip breadth (AC/HB), measured at regular exams, were used as indices of total adiposity and body fat distribution, respectively. Considering blood pressure as a continuous outcome variable (in models that allowed for intraclass correlation), the AC/HB ratio was significantly positively associated with both diastolic and systolic blood pressure (P < 0.001), adjusting for age and BMI. Blood pressure was dichotomized and hypertension risk was assessed using the proportional hazards model, adjusting for age and BMI. Seven hundred cases of hypertension were recorded by study physicians during 35,496 person-years of follow-up. The risk of hypertension increased approximately three-fold (95% confidence interval, 1.7 to 5.2) with a change of one unit in the AC/HB ratio. These estimates were little changed when the effects of smoking and alcohol intake were considered. Thus, the abdominal accumulation of body fat, apart from overall level of adiposity, was associated with both increased blood pressure and an increased risk of hypertension.

The sympathoadrenal system, obesity and hypertension: an overview

Obesity-related hypertension is a clinical problem of major significance. The nature of the relationship between blood pressure and body weight has not been elucidated. Recent studies suggest that insulin (and/or insulin resistance) may be involved. An hypothesis is developed, based on the relationship between dietary intake and sympathetic activity, that attributes obesity-related hypertension to sympathetic stimulation.

Regional distribution of body fat, plasma lipoproteins, and cardiovascular disease

Several epidemiological studies have reported that the regional distribution of body fat is a significant and independent risk factor for cardiovascular disease (CVD) and related mortality. Although these associations are well established, the causal mechanisms are not fully understood. Numerous studies have, however, shown that specific topographic features of adipose tissue are associated with metabolic complications that are considered as risk factors for CVD such as insulin resistance, hyperinsulinemia, glucose intolerance and type II diabetes mellitus, hypertension, and changes in the concentration of plasma lipids and lipoproteins. The present article summarizes the evidence on the metabolic correlates of body fat distribution. Potential mechanisms for the association between body fat distribution, metabolic complications, and CVD are reviewed, with an emphasis on plasma lipoprotein levels and plasma lipid transport. From the evidence available, it seems likely that subjects with visceral obesity represent the subgroup of obese individuals with the highest risk for CVD. Although body fat distribution is now considered as a more significant risk factor for CVD and related death rate than obesity per se, further research is clearly needed to identify the determinants of body fat distribution and the causal mechanisms involved in the metabolic alterations. It appears certain, however, that an altered plasma lipid transport is a significant component of the relation between body fat distribution and CVD.

Carotid artery atherosclerosis in cholesterol-fed female cynomolgus monkeys. Effects of oral contraceptive treatment, social factors, and regional adiposity

Female cynomolgus monkeys, a previously established model of carotid and coronary artery atherosclerosis, were used to study the relationships between potential risk factors and carotid artery atherosclerosis. Over a 24-month treatment period, one-third of the monkeys (n = 25) were given the oral contraceptive Ovral, one-third of the monkeys (n = 26) were given the oral contraceptive Demulen, and the remaining monkeys constituted a control group (n = 26). At necropsy, the atherosclerosis extent was measured in the left and right common carotid arteries and the left and right carotid bifurcations. Plasma lipid concentrations, regional adiposity, and social status were related to carotid artery atherosclerosis extent. The relationships between regional adiposity and social status and carotid artery atherosclerosis were accounted for, at least in part, by plasma lipid concentrations. Oral contraceptives had an adverse effect on plasma cholesterol concentrations and a protective effect against carotid artery atherosclerosis after adjusting for their effect on plasma lipids. The net result of these effects was little or no change in atherosclerosis extent in the carotid arteries due to oral contraceptive treatment.

Body fat and its distribution in relation to casual and ambulatory blood pressure

This study was undertaken to evaluate the associations of body fat and its distribution with casual and ambulatory blood pressure in nonobese men. One hundred and thirty-five normotensive or mildly hypertensive (but untreated) men employed at three work sites were studied. Casual blood pressure was measured at the work site at initial screening and on a second occasion by a nurse. Ambulatory blood pressure was measured noninvasively for 24 hours on a workday and analyzed as work, home, and sleep blood pressure measurements. Anthropometric measurements included height, weight, and waist and hip circumferences. Blood pressure was highest while at work; home blood pressure was higher than screening blood pressure or nurse blood pressure, and sleep blood pressure was lowest. Weight and both waist and hip circumferences (but not their ratio) were all significantly correlated with screening, nurse, and sleep blood pressures but not with work or home blood pressures. Stepwise regression analysis showed that waist circumference was the best overall predictor of blood pressure. We suggest that in situations where blood pressure is the dependent variable, correlations with other variables may be closest for "basal" measures of blood pressure and may be obscured by the effects of daily activities on blood pressure.

Relation between systemic hypertension and sleep hypoxaemia or snoring: analysis in 748 men drawn from general practice

OBJECTIVE

To establish whether a history of snoring or the degree of overnight hypoxaemia is an important independent predictor of systemic blood pressure.

DESIGN

Prospective community based study of blood pressure in relation to overnight oxygen saturation, height, weight, and a questionnaire assessment of snoring, smoking, and alcohol consumption. Analysis was by multiple linear regression techniques and analysis of variance.

SETTING

Small town outside Oxford, served by one group general practice of four partners. All measurements were made at home.

SUBJECTS

The names of 836 men aged 35-65 were drawn at random from the general practitioners' age and sex register and the men then asked to participate; 752 (90%) agreed.

MAIN OUTCOME MEASURES

Systolic, mean, and diastolic blood pressures and their association with age, obesity, alcohol consumption, cigarette consumption, snoring, and overnight hypoxaemia.

RESULTS

Though systemic blood pressure correlated significantly with overnight hypoxaemia, this was due to the cross correlation with age, obesity, and alcohol consumption. No independent predictive effect of overnight hypoxaemia was found. Snoring was correlated with systemic blood pressure but not significantly so and also was not an independent predictor once age, obesity, and alcohol consumption had been allowed for.

CONCLUSIONS

It is unlikely that snoring and sleep hypoxaemia from occult sleep apnoea are important causes of diurnal systemic hypertension when compared with age, obesity, and alcohol consumption. The increased prevalence of cardiovascular complications reported in snorers may be due to the confounding variable of obesity or to nocturnal rises in blood pressure that are not reflected in the daytime figures.

Relationship of fat mass and fat distribution to blood pressure

The relationship of fat mass, lean body mass (LBM), and fat distribution to blood pressure was examined in Japanese adult men and women. Percent body fat was estimated using two skinfold thicknesses, and fat mass and LBM were then calculated. Correlation coefficients showed that fat mass, fat distribution, and age were weakly associated with blood pressure levels, and that the correlation coefficients of LBM to blood pressure levels were nearly zero. Stepwise regression analysis revealed that fat mass and age contributed significantly to the variations in blood pressure levels. In addition, only in the case of men, trunk-extremity skinfolds ratio was also entered into the model for diastolic and mean arterial blood pressure. It thus has been concluded that fat mass may be the more predictive determinant of blood pressure level than LBM in the Japanese population, and that the independent correlation of fat distribution to blood pressure is rather small.

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.

Obesity hypertension

Obesity and hypertension are two major risk factors for the cardiovascular system. Whereas arterial hypertension increases afterload to the left ventricle, obesity produces an increase in stroke volume and increases preload. As a result of this double burden, the heart adapts with eccentric left ventricular hypertrophy. Contractility becomes impaired early in the course of obesity hypertension, and ventricular ectopy is observed. As a consequence, the obese hypertensive patient is at a high risk for congestive heart failure and sudden death. Despite the synergistic effects of obesity and hypertension on the heart, patients appear to be relatively protected from nephrosclerosis and coronary artery disease. These epidemiologic observations are supported by the pathophysiologic changes that take place in obesity hypertension. At any given level of arterial pressure, cardiac output and renal blood flow are elevated in obese hypertensive patients, whereas systemic and renal vascular resistance are decreased when compared to lean hypertensive patients. Because total peripheral resistance is considered the hemodynamic hallmark of arterial hypertension, systemic vascular complications may be less pronounced in obesity hypertension. Weight loss decreases preload, afterload to the left ventricle, and the sympathetic drive to the heart. Protecting the heart from these hypertrophic stimuli should be a major goal of preventive cardiology.

Body fat patterning and blood pressure in children and young adults. The Bogalusa Heart Study

The relationship of central body fat (measured by subscapular skinfold) and peripheral body fat (measured by triceps skinfold) to blood pressure was investigated in 3784 subjects aged 5 to 24 years old from the biracial community of Bogalusa, Louisiana. After adjustment for height, age, sex, and race, significant relationships were found for both central body fat (r = 0.19 and 0.14, p less than 0.0001) and peripheral body fat (r = 0.15 and 0.12; p less than 0.0001) with systolic and diastolic (fourth phase) blood pressure, respectively. However, the relationship between peripheral body fat and blood pressure, after controlling for the level of central body fat, was negligible (r = 0.00 and 0.01 for systolic and diastolic blood pressure, respectively). In contrast, the central body fat-blood pressure relationship remained statistically significant even after controlling for the peripheral body fat level. For central body fat, the partial correlations with systolic blood pressure were highest in young children (r = 0.15), dropped slightly during adolescence (r = 0.12), and became nonsignificant only in 18- to 24-year-old female subjects; correlations remained high in both black and white 18- to 24-year-old male subjects (r = 0.18 and 0.16, respectively). Mean levels of systolic blood pressure from the lowest to the highest quartile of central body fat ranged from 100.4 to 108.9 mm Hg. The adult hypertension-central body fat relationship, which has been shown by others, appears to exist in children. Continued efforts at early identification and prevention of obesity in children are warranted.

The association of body fat distribution with hypertension, hypertensive heart disease, coronary heart disease, diabetes and cardiovascular risk factors in men and women aged 18-79 years

To confirm the reported association of body fat distribution with cardiovascular disease, diabetes, blood pressure and serum cholesterol, data from the 1960-62 Health Examination Survey were analyzed. In this sample drawn from the noninstitutionalized population of the United States aged 18-79, mean values of two indices of upper versus lower body fat distribution increased steadily with age. Men had higher values than women, and black women had higher values than white women. Higher values of the indices were significantly associated with higher blood pressure, post-load serum glucose and greater prevalence of definite hypertension and definite hypertensive heart disease independent of multiple confounders. Associations with higher serum cholesterol and definite coronary heart disease prevalence were independent of overall ponderosity but not of age and multiple other confounders. Greater abdominal relative to lower body fat deposits were independently associated with increased cardiovascular risk in men and women, blacks and whites.

Insulin as a potential factor influencing blood pressure in amputees

War-injured, bilateral above-knee amputees are known to be at increased risk for cardiovascular mortality. To evaluate possible risk factors, we compared blood pressures and plasma glucose and insulin responses to orally administered glucose in 19 above-knee amputees from the Vietnam War (mean age, 36 +/- 1 years) with those of 12 age-matched unilateral below-elbow amputees. Body composition by densitometry and maximal oxygen consumption during arm or leg exercise were also determined. Nine of 19 leg amputees were hypertensive compared with one of 12 arm amputees. Their 3-hour average insulin responses were markedly increased (260 +/- 60 microU/ml) compared with those of normotensive leg (125 +/- 24 microU/ml) and arm amputees (101 +/- 20 microU/ml), and their mean body fat content (37.2%) also was elevated compared with that in both of these groups (23.2 and 22.6%, respectively). A unique finding was that both insulin response and body fat content were strongly and independently correlated with diastolic blood pressure (r = 0.55, p less than 0.01, and r = 0.62, p less than 0.01, respectively). We conclude that insulin may be a major factor in blood pressure regulation in the maturity-onset obesity that develops following traumatic leg amputation in young, healthy men.