Blood pressure and lipid profi le in young women : the role of anthropometric measurement

Marcelo Custódio RUBIRA Ana Paula Fernandes De Angelis RUBIRA Lucas De Angelis RUBIRA Milton Carlos Martins LIMA Roberto Jorge da Silva FRANCO Fernanda Marciano CONSOLIM-COLOMBO *Centro de Ciências da Saúde e do Desporto, Universidade Federal do Acre. * * F a c u l d a d e S ã o Lucas Porto Velho. * * * F a c u l d a d e d e Medicina, Universidade Estadual Paulista Botucatu. * * * * F a c u l d a d e d e Medicina, Universidade de São Paulo.


Introduction
Blood pressure and lipid profi le in young women: the role of anthropometric measurement e prevalence of obesity is increasing worldwide, and obesity is currently regarded as one of the most important public health problems of modern society.Obesity is considered to be a major risk factor for cardiovascular disorders according to the American Heart Association 1 .
In young subjects, the prevalence of obesity more than doubled over the past 15 years.Excessive adiposity in adolescents imposes an even larger risk for future development of cardiovascular diseases, relative to obesity developed in the adult life.Both central and global excessive adiposity may arise as a consequence of abnormality in the lipidic metabolism, being often associated with dyslipidemia and arterial hypertension 2 .Indeed, according to the National Institute of Health, obesity should be seen as a chronic degenerative disorder, since it increases the risks of early death even when it is minor.According to the National Institute of Health, risks are signi cantly elevated even for increased weight as low as from 2.3 to 4.5 kg above normal limits 3 .
Body composition has fundamental importance in the quality of life 4 and is a powerful predictor of mortality and morbidity in humans 5 .The identi cation and monitoring of the amount of body fat have been receiving special attention in aspects related to health promotion, not just for its actions in the prevention and in the control of cardiovascular diseases but also for their induction

Abstract
Body composition has fundamental importance in the quality of life and is a powerful predictor of mortality and morbidity in humans.The identifi cation and monitoring of the amount of body fat have been receiving special attention in aspects related to health promotion, not just for its actions in the prevention and in the control of cardiovascular diseases but also for their induction and association with risk factors, especially in the plasmatic lipid levels and arterial pressure.It was investigated the relationship between body mass index (BMI) and body fat percentage (%BF) by bioelectrical impedance analysis (BIA) with the blood pressure levels (systolic and diastolic) and serum lipids (TC, HDL-c, LDL-c, VLDL-c, TG).In a group of fi fty seven women (aged 18 to 26 years old ), obesity was detected in 5 and 19 women by BMI (≥ 30 kg/m 2 ) and %BF (≥ 30%), respectively.BMI and % BF were positively correlated with blood pressure (systolic and diastolic), and highly signifi cant in the obese group by %BF.Moreover, BMI and % BF were signifi cantly correlated with all lipids and lipoprotein fractions VLDL-c and triglyceride, respectively.These results suggest that %BF is a good indicator of "occult obesity" in subjects with normal body mass index.The associated use of BMI and %BF to better evaluate obesity may improve the study of blood pressure levels and serum lipid changes that are commonly associated with obesity.KEY WORDS: Body mass index; Bioelectrical impedance; Obesity; Blood pressure; Lipid.and association with risk factors, especially in the plasmatic lipid levels and arterial pressure [6][7] .
Variations in body fat content and regional fat distribution, whatever their origin is (genetic, acquired), seem to be potential candidates to explain, at least in part, the changes in cardiovascular risk pro le.
e excess accumulation body fat, in the central part of body and/or total body fat 8 , is a sign of abnormal lipid metabolism and is frequently associated with dyslipidemia and arterial hypertension 6,9 .e sympathetic nervous system seems to be activated in obesity 10 .However, this increased tonus is not homogenous for all tissues and organs.While the sympathetic activation is demonstrated at the level of the kidneys and skeletal muscles, cardiac sympathetic activity does not seem to be increased 11 .However, cardiac autonomic disturbances such as decreased vagal tonus, with or without sympathetic activation, are documented in obesity 12 .

Method
Subjects e most common estimate of body composition in populations has been the body mass index, which was actually developed as a measure of weight /height 2 and not as an index of obesity 13 .Its importance is due to values around 30 kg/m 2 (obese subjects) to correlate with high incidence of diseases, mainly arterial hypertension, lipid disorders -high cholesterol, triglyceride and cardiovascular diseases 14 .e bioelectrical impedance analysis (BIA) is an appropriate method for monitoring the body fat and superior to body mass index as measurement of the body composition 15 due to measure the content of fat into corporal mass.
In reason of the importance of recognizing subjects with high risk develop arterial hypertension and other metabolic disorders, and the operational simplicity of the anthropometric methods, the present work has an objective to correlate anthropometric index with the blood pressure and serum lipids.
Fifty seven white women, physiotherapy students, ranging in age from 18 to 26 years old were studied.e sample consisted of subjects without any medication, especially diet and known disease.
All participants signed an informed consent approved by the Ethics Committee.

Hemodynamic measures
Body mass index (BMI) was calculated as weight/ height 2 16 .Bioeletric resistance was measured with an Bioelectrical impedance analyzer (BIA-RJL Systems Model 101) using a standard tetrapolar technique according to the manufacturer's instructions and calibrated weekly with a 500 Ohm resistor.BIA is based on the principle that impedance to an electrical ow of an applied current is related to the volume of the conductor (the human body) and the square of the conductor's length (height).BIA results are based on the greater electrolyte content of the free mass and its greater conductivity of electricity compared with fat tissue.Bioelectrical impedance measurements were taken on the right side of the body with the subjects lying supine on a nonconductive surface in a room with normal ambient temperature.e skin was cleaned at the electrode sites with an alcohol pad.e sensor (proximal) electrodes were placed on the dorsal surface of the wrist so that the upper border of the electrode bisected the head of the ulna and on the dorsal surface of the ankle so that the upper border of the electrode bisected the medial and lateral malleoli.
e source (distal) electrodes were placed at the base of the second metacarpal-phalangeal and metatarsalphalangeal joints of the hand and foot .e researcher made certain that there were at least 5 cm between the proximal and distal electrode.e lead wires were then attached to the appropriate electrodes.e tester made certain that the subject's legs and arms were abducted approximately 45° to each other.ere was no contact between the thighs and between the arms and the trunk.Duplicated measurements were taken, and the average of the two measurements was used for calculating body fat percentage (%BF) 15 .If the %BF was o by more than 0.5%, the test was repeated until two readings were within 0.5%.e subjects were instructed not to ingest alcohol or ca eine 24 hours or exercise 12 hours before testing.Women were measured within 1 week after their menstrual cycles.
Arterial blood pressure was measured with a mercury sphygmomanometer, using the disappearance of Korotko sounds (phase V) as

Serum lipids analysis
In all subjects 10 ml venous blood was collected at 8:00 to 9:00 a.m. after an overnight fast.After collection of serum by centrifugation, serum total cholesterol (TC), high density lipoprotein cholesterol

Statistical analysis
The statistical analysis was performed using software SAEG (System Analysis Statistical Genetic).e 0.05 alpha level was adopted as criteria for statistical signi cance.Descriptive statistics (means and standard deviations) were calculated for all variables.Pearson's correlation coe cients were used to show the relationship between variables.

Results
The subjects characteristic is summarized in TABLE 1. e mean systolic (109 ± 9 mmHg) and diastolic (71 ± 7 mmHg) blood pressure were in normal limits for almost all subjects, and only 5 subjects had values in hypertensive level (above 140/90 mmHg in accordance with the classi cation of the Joint National Committee) 17  It is important to note that 49 subjects had values into normal limits (< 25 kg/m 2 ) when analyzed by BMI.However, the BIA detected 24 subjects with lipids metabolism disorders overweight (10 subjects) and obesity (14 subjects).e Pearson's correlation between blood pressure and anthropometric measurements are given in TABLE 3. Clearly, the values of BMI of all subjects correlated with systolic and diastolic blood pressure.When subgroups of subjects with di erent levels of BMI were analyzed, we can demonstrate that there were no correlation between the BMI and blood pressure values in the normal subgroup (25 kg/m 2 ), only in the overweight and obese group.
The %BF by BIA method tended to be signi cantly correlated with systolic and diastolic blood pressure when all subjects were analyzed.In analysis similar to that done in BMI, the %BF by BIA method in the normal subgroup there was no correlation, and in obesity group (%BF ≥ 30%) there was a stronger correlation with blood pressure.
It's important to note that, in the subgroup of the obese the %BF by BIA established better correlation with the blood pressure while BMI just was related with systolic pressure.a criteria for the determination of diastolic blood pressure.Arterial blood pressure was measured by a single observer in the right arm of seated participants.A rigorously standardized protocol was followed in which the participants were seated at least 10 minutes prior to the rst measurement and at least 2 minutes elapsed between three repeat measurements.Cu size was based on arm dimensions (cu were long enough to completely encircle the arm and wide enough to cover two-thirds the length of the upper arm).e values used in the present analysis are the means of all measurements realized 17 .
The total cholesterol level was measured by CHOD-PAP method, LDL-c by polyvinyl sulfate.
e HDL-c was separated with the phosphotungstic acid/magnesium chloride method.Triglyceride e VLDL-c were measured by the enzymatic colorimetric test (GOP-PAP method) 18 .e correlation between BMI and %BF all subjects were signi cant with all lipids and lipoprotein fractions, TC, VLDL-c and TG, respectively.
e BMI subgroup analysis demonstrates a loss of correlation for all di erent groups, including the ≥ 30 kg/m 2 group.Di erently, the %BF by BIA demonstrate a loss correlation in normal and overweight group but obese subjects was highly significant with lipoprotein fractions, HDL-c, TG,VLDL-c (TABLE 4).
So, it is relevant to note that 19 subjects detected by BIA as obese were considered normal by BMI.
is subgroup was called in the literature as "occult obese 24 .We veri ed this subgroup (occult obese) had a stronger correlation with a blood pressure and lipoprotein fractions HDL-c, TG, VLDL-c.

Variables
Women

Discussion
The importance of conducting studies in young subjects is demonstrated by the increasing prevalence of obesity in this population, and by the fact that minor excess fat developed at young ages imposes an even higher vascular risk than the onset of obesity in adulthoo 25 .
e main results of our study are the demonstration that there is a signi cant group of young women considered "normal" by BMI were already "occult obese" when evaluated by the BIA method 26 .Furthermore, in this group there was a strong correlation between %BF with blood pressure and serum lipid pro le.
Although the BMI is easy to use in population studies, it is not precise as a predictor of cardiovascular risk, since it may either over or underestimates the real proportion of fat.Additionally, BMI does not distinguish between fat weight and non-fat weight and does not allow inferences about the corporal distribution of fat 24 .
e importance of these results is that the regular use of BMI alone in analysis of body composition is not enough, there is a necessity of a more speci c method to improve the detection of lipid metabolic alterations, search as BIA.e "occult obesity" group was already suggested by F 27 when he studied more than 2,955 subjects.Although our group is small, we could nd similar results to that %BF by BIA is an appropriate index that better re ects serum lipids and blood pressure in "occult obesity", and may be a superior body mass index in these group.
We found that a signi cant proportion of subjects in our study had elevated fat proportion, while been classi ed as normal weight by the BMI.Based on the important recognition that excessive adiposity is linked to cardiovascular and metabolic disorders, anthropometric methods are recommended because of their accuracy and simplicity.
Anthropometric methods are of utility in several domains including epidemiological vigilance, scienti c investigation, individual and social health screenings, and should be particularly recommended for individuals that are not overweight or obese according to the BMI 8 .
Indeed, when more rigorous methods are used to measure the proportion of fat, it becomes patent that is faith itself and not absolute weight that increases cardiovascular risk.This is true not only for an important increase in fat proportion, but also for minor increases 28 .Indeed the importance of estimating the proportion of fat in predicting coronary diseases is supported by the work of Rimm and colleagues 29 .
Another important observation is that the associated use of BMI and %BF is best for evaluating lipid alterations and the obesity diagnoses, and it's correlation with blood pressure and serum lipid levels.The importance of body composition in the quality of life is well established.An inappropriate body composition can take many disorders in the human organism, for example the obesity and the malnutrition both associated with the development of several diseases 30 .
Obesity (≥ 30% BMI), excess accumulation of body fat, is a sign of abnormal lipid metabolism, and is an important predictor for hypertension, coronary heart disease, diabetes mellitus, hepato biliary disease 16 and frequently is associated with arterial hypertension and dyslipidaemia (high serum TG and low serum HDL-C rather than high serum TC and LDL-C) 8 .
Obesity is not a homogeneous disorder.In a subgroup of obese individuals, the sympathetic tonus is increased to key organs, including the kidney, muscles and peripheral vessels.Evidence for increased sympathetic tonus of the heart is less strong, especially in individuals without hypertension 11 .
Obese individuals are at increased risk of developing cardiac arrhythmia and sudden death when compared to normal weight individuals 31 .
In healthy animals, obesity induced by excessive feeding is associated with sympathetic activation and hypertension.Sympathetic activation is precociously induced by overfeeding, and is reversed by weight loss.Modi cation in the sympathetic system induced by overfeeding seems to precede alterations in the renin-angiotensin system 32 .
Subjects with lower levels of fat (overweight) show the same risks of heart disease, arterial hypertension and metabolic disorders when compare to that subjects with high and moderate percentage of fat body 3 .
e association of blood pressure with body weight could be due to the increased total body mass or some special underlying relationship between blood pressure and body fat 33 .
Our study and others studies as F 27 and N 24 suggested the existence of a subgroup of subjects with "occult obesity" that are not aware for their lipid alterations and blood pressure.Although the impact of this alteration in cardiac morbidity has not been studied yet, we can hypothetically suggest that this group could have a worth prognosis than people with normal lipid composition.More prospective studies with larger population with "occult obesity" are necessary to answer this point.
It is important to consider anthropometric measurements beyond the BMI.While we know its advantages in population studies, it does not distinguish body composition, and may underestimate or overestimate the actual percentage of fat, keeping us from strongly correlate with blood pressure, serum lipids and cardiovascular risk.A more thorough evaluation and careful body composition is required for prevention and health promotion.
e increased body fat was positively related to disorders in lipid metabolism and blood pressure elevation.However, further studies are needed to thoroughly clarify and de ne these relationships.

TABLE 1 -
Characteristics of subjects studied.

TABLE 2 -
Frequency distribution of BMI and %BF (BIA) in accordance with the classifi cation of the Consensus Latin American of obesity and with the works of Halpern; Guedes, Enzi.

TABLE 3 -
Pearson's correlation coeffi cients between anthropometric measurement and blood pressure.