TABLE 1.

Descriptive statistics on the sociodemographic composition of the China Health and Nutrition Survey sample¹

			2011
	2006: 9 provinces (n = 1134)	2009: 9 provinces (n = 1202)	9 provinces (n = 1047)	3 megacities (n = 363)
Female	46	45	48	50
Age, y	7.9 ± 0.1	10.4 ± 0.1*	11.8 ± 0.1*	12.3 ± 0.2**
Urbanicity index	59.8 ± 0.6	63.7 ± 0.5*	67.2 ± 0.6*	87.9 ± 0.6**
Household income, 2009 yuan	6352 ± 265	9007 ± 269*	10,305 ± 389*	16,122 ± 722**
Parental education
Less than secondary school	62	62	61	25**
Graduated from secondary school	28	29	29	32
Some college or greater	9	10	10	43**
Physical activity, METs2/wk	36.1 ± 1.5	46.0 ± 1.8*	48.0 ± 1.8*	55.2 ± 3.2**
Mean BMI-for-age z score3	−0.05 ± 0.04	−0.26 ± 0.04*	−0.22 ± 0.04*	0.33 ± 0.07**
Underweight	21	23	23	10**
Normal weight	64	64	63	65
Overweight/obese	15	13	14	24**
Consumers of snacks	39	53*	63*	80**
Per-capita energy from snacking, kcal/d	67 ± 4.8	94 ± 4.5*	102 ± 4.6*	183 ± 11.0**
Per-consumer energy from snacking, kcal/d	174 ± 10.6	179 ± 7.0	163 ± 6.3	231 ± 12.4**

¹Values are means ± SEs (continuous variables) or percentages. Snacking is defined as having reported consuming ≥1 snack over 3 d. Provinces are treated as repeated cross-sectional (2006, 2009, and 2011) and megacities are treated as cross-sectional (2011 only). *Percentage or mean is different in 2009 or 2011 relative to 2006 (for provinces sample only) with the use of 2-sample t tests, P < 0.05. **Percentage or mean is different between megacity and provinces (2011 only) with the use of 2-sample t tests, P < 0.05.

²MET, metabolic equivalent of task.

³From WHO growth standards (38).