fat is visible on physical examination because it is spread over the whole body,
visceral or abdominal fat is not apparent and obviously visible. Visceral fat,
however, is the most metabolically active fat in the body and is able to undergo
lipolysis quickly. Abdominal fat is surrounded by viscera and metabolic products,
e.g. triglycerides or free fatty acids are drained immediately into the portal
system and into the liver. Metabolic derangements in adults, e.g. dyslipidemia,
hyperinsulinemia and cardiac risk factors have been associated with the amount
of visceral fat.
Body mass index (BMI) is the preferred method of defining overweight
and obesity in childhood and adolescence. The BMI reflects the amount of body
fat and often is used for a proxy for measurement of body fatness in adults but
also in children and adolescents. Many studies investigating the association of
overweight and obesity with lipids and lipoproteins use the BMI as indirect
index of obesity and body fat. However, these results may not be comparable to
studies using direct measurements of (intra-abdominal) adipose tissue.
During the last years the role of body fat distribution, visceral body fat and
intra-abdominal fat and the relationship with specific risk factors in obese children
and adolescents has gained more and more interest.
Cohort studies in adults have shown that a preponderance of body fat in the
abdomen, upper body or trunk is predictive for cardiovascular heart disease and
diabetes and is associated with adverse levels of total cholesterol, LDL-cholesterol
as well as elevated triglycerides and low levels of HDL-cholesterol [23, 24].
Recent data indicate that body fat distribution, in particular abdominal body fat
distribution in adolescent girls is associated with an adverse risk factor profile
[3, 4, 25, 26]. However, the importance of fat distribution among children and
adolescents is less certain than in adults: negative and contradictory findings
are published and so far there is no conclusive evidence on the importance of
body fat distribution in childhood [27, 28]. The main reasons for this are the
difficulties in studying fat patterning in early life: there is only a small portion
of intra-abdominal fat present before adulthood [29], there are considerable
physiological changes in skinfold thickness during childhood and adolescence
[30], and anthropometric indices appropriate for use in adults are not suitable
in children [31]. Moreover, most anthropometric measures for body fat and fat
distribution are highly intercorrelated and it is not surprising that associations
with lipids are fairly similar.
Two recent studies examined the relation of body fat distribution and
cardiovascular risk factors: an analysis of the Bogalusa Heart study that
comprised 2,996 children and adolescents aged 5- to 17-years-old [17] and
investigated subscapular and triceps skinfolds, and waist/hip circumferences
with various risk factors (lipids, lipoproteins and insulin). In this study forward
stepwise regression was used to identify measures of body fat distribution
that best predicted the presence of risk factors. After adjusting for several
co-founding factors, e.g. age, sex, race, body weight and height, waist circumference
was significant for triglycerides, and HDL-cholesterol, subscapular
skinfold for LDL-cholesterol and triglycerides (table 2). Hip circumference
was only significant when waist circumference was present and triceps skinfold
provided no additional information. Central or abdominal distribution of
body fat was related to adverse concentrations of LDL-cholesterol, HDLcholesterol,
and insulin. These associations were observed whether fat patterning
was characterized by using waist circumference alone (after adjustment
for weight and height) or waist-to-hip ratio. Compared with a child at the 10th
percentile of waist circumference, a child at the 90th percentile was estimated
to have, on average, higher concentrations of LDL-cholesterol (0.17 mmol/l),
and lower concentrations of HDL-cholesterol ( 0.07 mmol/l). These differences,
which were independent of weight and height, were significant at the
0.001 level.
In a recent cross-sectional study, Maffeis et al. [26] studied the relationship
between anthropometric variables and lipid concentrations in a sample of 818
prepubertal children aged 3–11 years. To assess the clinical relevance of waist
circumference in prepubertal children height, weight, triceps and subscapular
skinfolds, and waist circumference were measured and plasma levels for total
cholesterol, HDL-cholesterol, LDL-cholesterol, apolipoprotein A1 (ApoA1),
and apolipoprotein B (ApoB) were determined. A multivariate linear model
analysis showed that ApoA1/ApoB, HDL-cholesterol, total cholesterol/HDLcholesterol,
and systolic as well as diastolic blood pressure were significantly
associated with waist circumference and triceps and subscapular skinfolds,
independent of age, gender, and body mass index.
Therefore, there seems to be growing evidence that the assessment of
body-fat distribution could identify subjects with the highest risk of adverse
lipid profile and hypertension. Waist circumference as well as subscapular and
triceps skinfolds may be helpful parameters in identifying prepubertal children
with an adverse blood lipid profile and hypertension. Waist circumference,
which is easy to measure and more easily reproducible than skinfolds, therefore
may be considered in clinical practice.
0 komentar:
Posting Komentar