Table 1.

Descriptive statistics of participants in the sample

	Total (n=568)		Normal leptin levels (n=485)		Hyperleptinaemia (n=83)		p Value*
	Mean or number	(SD) or percentage	Mean or number	(SD) or percentage	Mean or number	(SD) or percentage
Chronological age
Age (years)	16.8†	(0.3)	16.8†	(0.3)	16.8†	(0.3)	NS
Sex
Male	287	50.5	231	47.6	56	67.5	0.001‡
Female	281	49.5	254	52.4	27	32.5
Serum leptin
Males (μg/L)	6.0†	(9.6)	2.2†	(1.9)	21.40†	(13.1)	<0.0001
Females (μg/L)	19.4†	(14.4)	16.0†	(9.7)	51.32†	(12.7)	<0.0001
Anthropometrics
Height at 16 years (WHO z-score)	−0.45†	0.8	−0.47†	0.8	−0.35†	0.8	NS
Height at 16 years (CDC percentile)	35.0†	24.7	34.5†	24.7	37.8†	24.2	NS
BMI at 16 years (WHO z-score)	0.63†	(1.2)	0.47†	(1.1)	1.58†	(1.3)	<0.0001
BMI at 16 years (CDC percentile)	64.4†	28.0	61.4†	27.4	81.4†	25.3	<0.0001
Weight status
Normal weight	352	61.9	329	67.8	23	27.7	<0.0001
Overweight	139	24.5	115	23.7	24	28.9
Obesity	77	13.6	41	8.5	26	43.4
Insulin sensitivity
HOMA-IR	1.77†	(1.2)	1.64†	(1.0)	2.39†	(1.9)	<0.0001
IR	83	14.6	59	12.5	24	25.3	<0.0001‡
PA patterns
Weekly scheduled PA≤90 min	322	56.7	275	56.7	47	56.6	NS‡
Diet habits
Unhealthy diet	162	28.5	137	28.3	25	30.1	NS‡
Parental education
Mother's schooling: incomplete secondary	377	34.0	168	34.6	25	30.1	NS‡
Father's schooling: incomplete secondary	159	28.0	140	28.9	19	22.9	NS‡
Type of secondary education
Adult school	98	17.3	79	16.3	19	22.9	NS‡
Iron supplementation (infancy)
Non-added Fe	238	41.9	205	42.3	33	39.8	NS‡

Normal weight: BMI z-score ≤1 SD; overweight: BMI z-score >1 and ≤2 SD; obesity: BMI z-score >2 SD.

Hyperleptinaemia defined according to the cut-offs published by Köster-Weber et al.

*Student's t-test, except as indicated.

†Values expressed as mean and (SD). Otherwise, values are number of observations and percentage.

‡χ² test (Pearson).

BMI, body mass index; CDC, Centers for Disease Control and Prevention; HOMA, homeostasis model assessment of IR; IR, insulin resistance; NS, not significant; PA, physical activity.