Table 2.

Comparison in body mass index (BMI) Z-scores between menstruating (post-) and non-menstruating (pre-) adolescent girls by the characteristics of adolescent girls

	BMI Z-scores, Mean ± SD		P a
	Pre-	Post-
Education
< 6	−1.10 ± 0.78	−0.57 ± 0.77	0.19
6–9	−1.15 ± 1.01	−0.30 ± 0.81	<0.01
> 9		−0.33 ± 0.88b
Family size
< 3		−0.05 ± 0.69b
3–5	−1.18 ± 1.05	−0.29 ± 0.81	<0.01
> 5	−1.12 ± 0.91	−0.58 ± 0.84	0.03
Source of income
Farming only	−1.13 ± 0.83	−0.37 ± 0.79	<0.01
Farming plus others	−1.5 ± 0.78	−0.43 ± 0.86	<0.01
Others	−0.90 ± 1.26	−0.23 ± 0.82	0.01
Rural and urban
Urban	−1.08 ± 1.16	−0.19 ± 0.83	<0.01
Rural	−1.20 ± 0.97	−0.36 ± 0.81	<0.01
Geography site
Northern plateau	−1.22 ± 1.23	−0.40 ± 0.91	<0.01
Central Shaanxi	−1.15 ± 1.01	−0.30 ± 0.81	<0.01
Southern region	−1.21 ± 0.77	−0.27 ± 0.71	<0.01

^aTwo-sample t-test was used to examine differences between pre- and post- menstruating

^bNo subjects were observed in non-menstruating (pre-) category