Definition Lipids and Lipoproteins in Childhood Obesity

Prevalence of obesity in children and adolescents has increased during the
last decades in almost all countries worldwide. From cross-sectional and longitudinal
studies of many countries and different ethnic groups there is ample
evidence that obesity in children and adolescents is associated with altered
lipids and lipoproteins and with other well-known risk factors for cardiac disease
in adulthood, e.g. insulin and blood pressure.
Among cardiovascular risk factors which are associated with increased
morbidity and mortality lipids and lipoproteins are of special importance and in
many studies childhood obesity has been shown to be associated with increased
levels of total cholesterol, LDL-cholesterol and triglycerides and decreased levels
of HDL-cholesterol [1–4]. However, the degree of obesity is consistently more
strongly associated with HDL-cholesterol and abnormal lipid profile in male
adolescents than in female adolescents [5, 6].
Recent data clearly show the importance of body fat distribution and in
particular of visceral fat even in the adolescent age group [3, 7–9].
The importance of increased lipids and lipoproteins is underlined by the
fact that tracking of unfavorable lipid levels from childhood and adolescence to
adulthood was reported in several longitudinal studies [10–13], and moreover
by the fact that obesity in early life is associated with early stages of atherosclerosis
[14].
Weight reduction, which often results in normalization of increased lipids
and lipoproteins [15, 16], is therefore an important factor in the treatment of
obese children and adolescents in order to postpone negative health effects in
adulthood.
Prevalence of Elevated Lipids and Lipoproteins
in Childhood Obesity
In many studies, childhood obesity has been shown to be associated with
altered levels of lipids and lipoproteins, and obesity increases the likelihood of
elevated concentrations of total cholesterol, LDL-cholesterol and triglycerides
and low levels of HDL-cholesterol.
In The Cardiovascular Risk in Young Finns Study, in children and adolescents
aged 3–18 years not only serum insulin was correlated positively with
BMI but also serum triglycerides and HDL-cholesterol were inversely correlated
with obesity [1, 2].
In seven cross-sectional studies conducted by the Bogalusa Heart Study
between 1973 and 1994 obesity (Quetelet index: 95th percentile) in 5- to
17-year-old children was associated with elevated LDL-cholesterol and triglycerides
and decreased HDL-cholesterol. Although the sensitivity (23–62%) and
positive predictive value (9–24%) of overweight was generally low for each risk
factor, many of the ORs were substantial. Overweight schoolchildren with a
Quetelet index 85th percentile were 2.4 times as likely to have an elevated
level of total cholesterol as normal-weight children, and the odds ratios for
other associations were 3.0 for LDL- cholesterol, 3.4 for HDL-cholesterol and
7.1 for triglycerides [17]. Table 1 shows the results of the study in whites and
the differences in gender, which were not significant. Most associations tended
to be stronger among whites than among blacks but there were no significant
differences for lipids and lipoproteins.
In general, various measures of overweight and obesity have been found to
be related weakly to levels of total cholesterol and LDL-cholesterol
(r 0.05–0.15), [5, 18–21] but more strongly to levels of HDL-cholesterol and
triglycerides [5, 18, 19, 21, 22]. Although the results generally agree well within
the investigations, comparisons across studies can be influenced by differences
in the age and race distribution of the sample, the specific weight-height index
or skinfold thickness, and the statistical techniques used.

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