Introduction:Childhood obesity is a growing health problem worldwide. Body mass index (BMI) has been used as the main measurement of obesity for years but its quality for children has been questioned. In 2011 the Health School was formed at the Childrens Medical Center at Landspitali University Hospital for treatment of obese children and their families. The aim of this study was to find the best predictor of blood test abnormalities and to get a clear picture of abnormalities in blood values in the group of obese children referred to the Health School.
Methods:All children referred to the Health School from January 1st 2011 until March 15th 2013 were retrospectively studied (n=181). Information was gathered on height, weight, BMI, waist circumference and available blood variables.
Results:Abnormal blood values were found in 54 cases (47%). Of the children where information was available, four (4%) had Non-Alchoholic Fatty Liver Disease (NAFLD) and 28 (28%) had a raised fasting insulin levels whereof 8 (8%) needed treatment. One child had both NAFLD and raised fasting insulin.
Conclusion: Abnormal blood values are common in obese children. Waist circumference appears to have a better predictive value of these abnormalities than BMI-SDS. Waist circumference could be used to screen for children who need physician supervision because of risk of metabolic disorders. Waist circumference adds important information to the risk assessment of obese children. This study emphasises the importance of care givers measuring waist circumference in obese children.

 

Table I. Participant characteristics before treatement

	Girls		Boys
Column1	n	Average ± SD	n	Average ± SD
Age (years)	101	11.2 ± 2.9	78	12.1 ± 2.7
Height (cm)	101	151.1 ± 15.5	78	157.1 ± 15.6
Weight (kg)	101	72.0 ± 23.9	78	78.9 ± 25.5
Weight SDS	101	4.6 ± 1.3	78	4.3 ± 1.2
BMI (kg/m2)	101	30.5 ± 5.5	78	31.0 ± 5.0
BMI-SDS	101	3.3 ± 0.7	78	3.7 ± 0.8
WC (cm)	62	101.3 ± 12.4	48	104.1 ± 14.8
WC SDS	62	3.3 ± 0.4	48	2.8 ±  0.3
WHtR	62	0.66 ± 0.05	48	0.66 ± 0.06
WHtR SDS	62	3.1 ± 0.3	48	3.0 ± 0.3

BMI (Body Mass Index), BMI-SDS (BMI standard deviation score), WC (Waist Circumference), WC SDS (WC standard deviation score), WHtR (Waist-to-Height Ratio), WHtR SDS (WHtR standard deviation score)

Table II. Results and cut-off points for abnormalities of blood values^{16, 24-30} (1)

Blood test	n	Median (5-95 span)	Min-max	Cut-off points for abnormalities	Number of abnormal values (%)	Provides informations about
serum insulin	100	17.9 (5-51.2)	0.2-71.4	≥25.0 µU/L	28 (28)	Insulin resistance, type 2 diabetes, a risk factor for coronary heart disease24, 26
serum glucose	81	4.9 (4.4-5.6)	4.1-5.8	≥5.6 mmol/L	6 (7)	Insulin resistance, diabetes29
serum ALAT	102	30.0 (15.1-60.5)	6.0-147.0	>45.0 U/L	9 (9)	NAFLD, predictive value of diabetes25, 27, 28
serum TSH	112	2.6 (1.2-5.3)	0.4-10.1	>4.2 mU/L	14 (13)	Elevated TSH and decreased T4 are a sign of hypothyroidism. 29
serum free T4	104	15.1 (11.8-19.2)	11.2-24.2	<12.0 eða >22.0 pmol/L	7 (7) <12.0, 1 (1) >22.0
serum cholesterol	102	4,4 (3,6-5,9)	3.2-6.3	>6.0 mmol/L	1 (1)	A risk factor for coronary heart disease26
serum HDL	98	1,2 (0,9-1,8)	0.7-2.2	<1.0 mmol/L	15 (15)	Ratio between HDL and LDL is a risk factor for coronary heart disease26
serum triglyceride	98	1,0 (0,5-2,4)	0.4-3.6	>1.6 mmol/L	12 (12)	Metabolic syndrome, NAFLD, a risk factor for coronary heart disease16, 30

ALAT (Alanine aminotransferase), TSH (Thyroid stimulating hormone), FT4 (free thyroxine), HDL (High-density lipoprotein), NAFLD (Non-alchoholic fatty liver disease).

Table III. Comparisonbetween participants with hyperinsulinema or NAFLD and other participants in the Health School

	Hyperinsulinemia or NAFLD n= 11	Other children n= 169
	Average ± SD or % (n)	Average ± SD or % (n)	Difference
Girls	36.4 (4)	57.4 (97)
Height (cm)	168.9 ± 11.9	152.5 ± 15.8	16.4**
Weight (kg)	103.7 ± 19.6	72.9 ± 24.1	30.8**
Weight SDS	5.8 ± 0.8	4.4 ± 1.2	1.4**
Age (years)	13.2 ± 2.2	11.4 ± 2.9	1.8*
BMI (kg/m2)	35.7 ± 3.7	30.4 ± 5.2	5.3**
BMI SDS	4.0 ± 0.7	3.4 ± 0.8	0.6*
WC (cm)	118.4 ± 7.6	100.9 ± 13.7	17.5**
WC SDS	3.3 ± 0.4	3.1 ± 0.4	0.2
WHtR	0.69 ± 0.04	0.66 ± 0.06	0.03
WHtR SDS	3,2 ± 0,2	3,1 ± 0,3	0,1

 * p <0.05

**p <0.01

BMI (Body Mass Index), BMI-SDS (BMI standard deviation score),  WC (Waist Circumference), WC SDS (WC standard deviation score), WHtR (Waist-to-Height Ratio), WHtR SDS (WHtR standard deviation score)

Table IV. Correlation between blood values and obesity measurements and age

	Weight SDS r	BMI-SDS r	WC SDS r	WHtR SDS r	Age r
se-insulin	0.41**	0.20**	0.25**	0.25**	0.43**
se-glucose	0.17	0.02	0.15*	0.10	0.25
se-ALAT	0.22*	0.29**	0.12	0.14	0.12*
se-cholesterol	-0.22	-0.27*	-0.20	-0.24	-0.02
se-HDL	-0.06	0.02	-0.12	-0.22*	-0.39**
se-triglyceride	0.07	0.01*	0.09	0.17	0.34**

*p<0,05

**p<0,01

WC (Waist Circumference), WHtR (Waist-to-Height Ratio), ALAT (Alanine aminotransferase), TSH (Thyroid stimulating hormone), HDL (High-density lipoprotein), T4 (Thyroxine).

ALAT (Alanine aminotransferase), TSH (Thyroid stimulating hormone), HDL (High-density lipoprotein), T4 (Thyroxine).