Characteristics of the study participants
The general characteristics of participants in three rounds of CHNS (1991, 2004, 2015) are presented in Table 1. This study was conducted on 3730, 2866, and 3623 WCA in 1991, 2004, and 2015, respectively. Marital status, education level, income, BMI, PA, region, district, and drinking behavior showed significant temporal trends across three rounds of surveys (p < 0.001). From 1991 to 2015, urban participants increased from 14.1–22.9% and the mean BMI increased from 21.8 kg/m2 to 23.5 kg/m2, while the mean PA decreased from 462.6 METs/w to 166.6 METs/w. Participants who are married, or have a higher education level became more prevalent over time (p < 0.001). The smoking status of WCA was relatively stable, but the drinking status increased significantly over time (p < 0.001). The proportion of WCA from eastern China increased notably from 1991 to 2015 (p < 0.001).
Table 1
General Characteristics of WCA by CHNS Rounds, 1991-20151-2.
Characteristic
|
1991
|
2004
|
2015
|
P-value
|
Sample(N)
|
3730
|
2866
|
3623
|
-
|
Education level (%)
|
|
|
|
|
Primary school/below
|
51.6 (0.8)
|
35.2 (0.9)
|
18.1 (0.7)
|
< 0.001
|
Middle school
|
32.1(0.8)
|
36.1(0.9)
|
37.4(0.9)
|
< 0.001
|
High school/above
|
16.3 (0.6)
|
28.7(0.8)
|
44.5 (0.9))
|
< 0.001
|
Marital status (%)
|
|
|
|
|
Single
|
23.8(0.7)
|
14.2(0.7)
|
11.50.6)
|
< 0.001
|
Married
|
76.2(0.7)
|
85.8(0.7)
|
88.5(0.6)
|
< 0.001
|
Income (1k yuan)
|
3.8 (0.1)
|
8.9 (0.2)
|
44.8 (1.4)
|
< 0.001
|
BMI (kg/m2)
|
21.8(0.1)
|
22.8(0.1)
|
23.5 (0.1)
|
< 0.001
|
PA(METs/w)
|
462.6 (4.6)
|
246.0(4.0)
|
166.6(2.8)
|
< 0.001
|
Smoking (%)
|
2.0(0.1)
|
2.7(0.1)
|
3.0 (0.1)
|
0.507
|
Drinking (%)
|
12.0 (0.6)
|
9.3(0.7)
|
7.2(0.7)
|
< 0.001
|
Region (%)
|
|
|
|
|
Urban
|
14.1(0.6)
|
13.9(0.6)
|
22.9 (0.7)
|
< 0.001
|
Rural
|
85.9(0.6)
|
86.1(0.6)
|
77.1(0.7)
|
< 0.001
|
District (%)
|
|
|
|
|
Eastern
|
35.8(0.8)
|
44.7(0.9)
|
46.0(1.0)
|
< 0.001
|
Central
|
38.2(0.8)
|
33.3(0.9)
|
26.0(0.8)
|
< 0.001
|
Western
|
26.0(0.7)
|
22.0(0.8)
|
28.0(0.9)
|
< 0.001
|
1 Mean percentage and standard error(SE)in parentheses,2 There were significant trends in each subgroup over the survey round, except for smoking status.
Trends in energy intake and macro-nutrient composition
Table 2 shows the secular trends of dietary energy and macronutrient composition among Chinese WCA from 1991 to 2015. The dietary fat intake of these participants increased notably from 62.1 g/d to 72.9 g/d over time. However, the average intake of dietary energy, protein, and carbohydrate decreased significantly from 2241.1 kcal/d, 73.8 g/d, and 421.2 g/d in 1991 to 1870.1 kcal/d, 58.5 g/d, and 244.4 g/d in 2015, respectively. Additionally, from fat increased from 24.5–34.6%, whereas %E from carbohydrates decreased from 63.1–52.5% over time.
Table 2
Trends of the Dietary Energy and Macronutrient Composition of WCA by CHNS Rounds,1991-20151-4.
Dietary Intake
|
1991
|
2004
|
2015
|
P-value
|
Energy(kcal/d)
|
2241.1(11.0)
|
2080.9(11.3)
|
1870.1 (14.2)
|
< 0.001
|
Fat(g/d)
|
62.1 (0.7)
|
66.6 (0.7)
|
72.9 (0.9)
|
< 0.001
|
Protein(g/d)
|
73.8(0.4)
|
63.7(0.4)
|
58.5(0.4)
|
< 0.001
|
Carbohydrate(g/d)
|
421.2 (2.2)
|
306.2(1.9)
|
244.4 (2.2)
|
< 0.001
|
Fat(%E)
|
24.5 (0.2)
|
28.0 (0.2)
|
34.6 (0.2)
|
< 0.001
|
Carbohydrate(%E)
|
63.1(0.2)
|
59.6(0.2)
|
52.5(0.2)
|
< 0.001
|
1 Mean percentage and standard error(SE)in parentheses, 2 %E, percentage of dietary energy intake.3 Values adjusted for, marital status, education, income, BMI, PA, smoking, drinking, region, and district, 4 Significant trends in each sub-group across all survey years.
As seen in Table 3, the dietary energy, protein, carbohydrate intakes, and %E from carbohydrates showed a significant downward trend while the dietary fat intake and En% from fat showed a notable increasing trend over time, regardless of districts and regions in China (p < 0.001). In 2015, WCA in urban western China had the most dietary fat intake (89.5g/d) and the most %E from fat (41.4%), while they had the least dietary carbohydrate intake (205.9 g/d) and the least %E from carbohydrate (44.4%). Moreover, WCA in rural western China had the least intake of dietary protein (60.5 g/d) in 2015.
Table 3
Trends in the dietary energy and macronutrient composition by region and district from CHNS Round,1991–20151−4
|
Overall
|
Urban
|
Rural
|
1991
|
2004
|
2015
|
p-trend
|
1991
|
2004
|
2015
|
p-trend
|
1991
|
2004
|
2015
|
p-trend
|
Eastern
|
|
|
|
|
|
|
|
|
|
|
|
|
Energy(kcal/d)
|
2529.0(17.2)
|
2006.0(16.6)
|
1857.3(11.1)
|
0.000
|
2286.6 (21.3)
|
1951.5(17.1)
|
1846.7(16.9)
|
0.000
|
2563.0(18.3)
|
2013.1(17.8)
|
1865.0(24.0)
|
0.000
|
Fat(g/d)
|
62.6(1.0)
|
68.1(1.1)
|
71.8(1.1)
|
0.000
|
76.4(2.7)
|
75.8(3.3)
|
73.6(1.8)
|
0.000
|
60.7(1.1)
|
67.1(1.1)
|
70.5(1.4)
|
0.000
|
Protein(g/d)
|
75.1(0.6)
|
66.6(0.6)
|
64.7(0.7)
|
0.000
|
71.8(1.6)
|
68.0(2.0)
|
67.4(1.1)
|
0.000
|
75.6(0.7)
|
65.8(0.6)
|
62.7(0.9)
|
0.000
|
Carbohydrate(g/d)
|
415.7(3.5)
|
286.2(2.7)
|
236.9(2.7)
|
0.000
|
327.7(4.5)
|
248.9(2.3)
|
226.9(3.6)
|
0.000
|
428.0 (3.7)
|
291.1(2.9)
|
244.2(3.9)
|
0.000
|
Fat(%E)
|
22.1(0.3)
|
30.7(0.3)
|
34.2(0.3)
|
0.000
|
26.5(0.6)
|
34.8(1.0)
|
35.0(0.4)
|
0.000
|
21.5(0.3)
|
30.1(0.4)
|
33.7(0.4)
|
0.000
|
Carbohydrate(%E)
|
65.4(0.3)
|
57.0(0.3)
|
51.4(0.3)
|
0.000
|
60.1(0.6)
|
56.2(0.9)
|
49.8(0.4)
|
0.000
|
66.2(0.3)
|
57.7(0.4)
|
52.6(0.4)
|
0.000
|
Central
|
|
|
|
|
|
|
|
|
|
|
|
|
Energy(kcal/d)
|
2626.7(19.1)
|
2144.3(20.6)
|
1964.0(25.7)
|
0.000
|
2222.9(28.7)
|
2106.8(20.3)
|
1950.3(27.5)
|
0.000
|
2703.7(21.2)
|
2151.0(22.1)
|
1970.8(20.0)
|
0.000
|
Fat(g/d)
|
61.9(1.2)
|
66.6(1.3)
|
79.8(1.7)
|
0.000
|
74.0(2.6)
|
82.7(2.5)
|
89.3(2.9)
|
0.000
|
59.6(1.3)
|
63.7(1.3)
|
74.4(2.1)
|
0.000
|
Protein(g/d)
|
75.8(0.6)
|
66.4(0.8)
|
62.4(0.9)
|
0.000
|
68.3(1.3)
|
69.0(1.8)
|
64.3(1.5)
|
0.000
|
77.2(0.7)
|
65.9(0.9)
|
61.5(1.1)
|
0.000
|
Carbohydrate(g/d)
|
441.3.(3.8)
|
319.2(3.5)
|
248.5(4.5)
|
0.000
|
320.0(5.0)
|
269.9(5.8)
|
218.8(5.4)
|
0.000
|
464.4(4.1)
|
327.9(3.6)
|
263.3(6.1)
|
0.000
|
Fat(%E)
|
26.0(0.4)
|
27.1(0.4)
|
36.5(0.4)
|
0.000
|
30.3(0.7)
|
32.4(1.1)
|
41.0(0.8)
|
0.000
|
25.2(0.4)
|
26.6(0.5)
|
34.2(0.6)
|
0.000
|
Carbohydrate(%E)
|
61.8(0.4)
|
62.8(0.4)
|
50.5(0.5)
|
0.000
|
57.1(0.7)
|
53.7(1.0)
|
45.6(0.8)
|
0.000
|
62.7(0.4)
|
64.5(0.5)
|
52.9(0.6)
|
0.000
|
Western
|
|
|
|
|
|
|
|
|
|
|
|
|
Energy(kcal/d)
|
2426.0(19.5)
|
2136.5(22.4)
|
1916.3(23.6)
|
0.000
|
2089.1(17.4)
|
2003.3(14.4)
|
1891.1(10.2)
|
0.000
|
2482.8(17.8)
|
2162.5(15.6)
|
1932.5(20.0)
|
0.000
|
Fat(g/d)
|
61.8(1.0)
|
67.7(0.9)
|
85.6(1.0)
|
0.000
|
65.2(3.1)
|
74.1(3.4)
|
89.5(1.3)
|
0.000
|
61.2(1.3)
|
66.7(1.5)
|
83.1(2.0)
|
0.000
|
Protein(g/d)
|
68.6(0.6)
|
63.7(1.0)
|
62.1(0.9)
|
0.000
|
65.5(0.6)
|
66.8(0.6)
|
64.6(0.7)
|
0.000
|
69.2(0.7)
|
63.1(1.1)
|
60.5(1.1)
|
0.000
|
Carbohydrate(g/d)
|
398.2(3.9)
|
326.7(3.8)
|
223.5(3.3)
|
0.000
|
309.2(3.5)
|
267.0(2.6)
|
205.9(3.6)
|
0.000
|
413.2(4.2)
|
338.3(4.1)
|
235.1(3.6)
|
0.000
|
Fat(%E)
|
25.6(0.4)
|
28.3(0.5)
|
39.7(0.4)
|
0.000
|
30.8(0.3)
|
34.7(0.3)
|
41.4(0.4)
|
0.000
|
24.6(0.4)
|
27.0(0.5)
|
38.6(0.6)
|
0.000
|
Carbohydrate(%E)
|
61.8(0.4)
|
60.0(0.5)
|
47.0(0.4)
|
0.000
|
55.4(0.8)
|
52.2(0.9)
|
44.4(0.6)
|
0.000
|
62.9(0.4)
|
61.6(0.3)
|
48.9(0.4)
|
0.000
|
1 Mean percentage and standard error (SE)in parentheses,2%E, percentage of dietary energy intake, 3 Values adjusted for, marital status, education, income, BMI, PA, smoking, drinking, 4 Significant trends in each sub-group across all survey years.
As seen in Fig. 1, the proportion of WCA with more than 30% of energy from fat and less than 50% of energy from carbohydrates increased notably from 1991 to 2015, regardless of location and region (p < 0.001). The average proportion of participants with higher fat intake compared with the DRIs increased from 27.3–70.1%. Specifically, the proportion with the higher fat intake increased from 24.5–66.7%, and from 44.7–75.5% in rural and urban participants, respectively. In addition, the proportion with lower carbohydrate intake increased from 11.7–45.8%, and from 18.2–60.0% in rural and urban participants, respectively. In 2015, WCA in urban western China had the most proportion who consumed more than 30% of energy from fat (81.7%) and less than 50% of energy from carbohydrates (72.1%).
Trends of urban-rural disparities
As seen in Table 4, urban-rural disparities in dietary energy and carbohydrate intake of WCA decreased significantly over time across all regions and locations in China (p < 0.001). Generally, WCA from the urban had less dietary energy and carbohydrate intake than their rural counterparts. However, WCA from the rural areas had more dietary protein intake than their urban participants in 1991, while urban participants had more in 2004, and this value increased further in 2015. The average urban-rural disparities in dietary protein intake were 4.0 g/d among WCA in 2015.It is worth noting that the average urban-rural differences in dietary fat in eastern China decreased from 15.7 g/d to 3.2 g/d over time while the differences increased from 14.5 g/d to 16.4 g/d in the central district, and from 4.0 g/d to 6.3 g/d in western China. In 2015, the average urban-rural disparities in dietary fat and carbohydrate intake were 8.1 g/d and 30.5 g/d among WCA, respectively.
Table 4
Trends of the Urban-Rural Disparities in the Energy and Macronutrient Composition by region and district from CHNS Round,1991–20151−5
|
1991
|
2004
|
2015
|
p-trend
|
Urban- rural
|
P-value
|
Urban- rural
|
P-value
|
Urban- rural
|
P-value
|
Eastern
|
|
|
|
|
|
|
|
Energy(kcal/d)
|
-277.0(4.6)
|
0.000
|
-61.6(2.6)
|
0.000
|
-18.3(1.6)
|
0.227
|
0.000
|
Fat(g/d)
|
15.7(3.0)
|
0.000
|
8.8(0.6)
|
0.008
|
3.2(0.3)
|
0.162
|
0.000
|
Protein(g/d)
|
-3.8(0.6)
|
0.000
|
3.2(0.6)
|
0.000
|
4.7(0.5)
|
0.001
|
0.000
|
Carbohydrate(g/d)
|
-100.3(5.6)
|
0.000
|
-42.2(0.4)
|
0.000
|
-17.3(1.4)
|
0.002
|
0.000
|
Fat(%E)
|
5.0(0.6)
|
0.000
|
4.7(0.3)
|
0.000
|
1.3(0.6)
|
0.039
|
0.000
|
Carbohydrate(%E)
|
-6.1(0.7)
|
0.000
|
-6.5(0.1)
|
0.000
|
-2.7(0.6)
|
0.000
|
0.000
|
Central
|
|
|
|
|
|
|
|
Energy(kcal/d)
|
-480.8(1.7)
|
0.000
|
-44.2(1.1)
|
0.000
|
-20.5(0.5)
|
0.707
|
0.000
|
Fat(g/d)
|
14.5(0.8)
|
0.000
|
16.0(1.3)
|
0.000
|
16.4(0.1)
|
0.000
|
0.000
|
Protein(g/d)
|
-8.9(0.9)
|
0.000
|
3.1(0.2)
|
0.038
|
3.8(0.1)
|
0.136
|
0.000
|
Carbohydrate(g/d)
|
-144.4(1.7)
|
0.000
|
-58.0(0.8)
|
0.000
|
-44.5(0.4)
|
0.000
|
0.000
|
Fat(%E)
|
5.1(0.76)
|
0.000
|
5.8(0.2)
|
0.000
|
6.8(0.3)
|
0.000
|
0.000
|
Carbohydrate(%E)
|
-5.6(0.8)
|
0.000
|
-10.8(0.4)
|
0.000
|
-7.4(0.7)
|
0.000
|
0.000
|
Western
|
|
|
|
|
|
|
|
Energy(kcal/d)
|
-393.7(2.9)
|
0.000
|
-159.2(1.0)
|
0.009
|
-41.0(0.8)
|
0.396
|
0.000
|
Fat(g/d)
|
4.0(0.6)
|
0.000
|
5.4(0.4)
|
0.001
|
6.3(0.5)
|
0.028
|
0.000
|
Protein(g/d)
|
-3.7(0.7)
|
0.036
|
3.7(0.1)
|
0.000
|
4.2(0.1)
|
0.019
|
0.000
|
Carbohydrate(g/d)
|
-119.9(1.8)
|
0.000
|
-71.1(0.7)
|
0.000
|
-29.2(0.2)
|
0.000
|
0.000
|
Fat(%E)
|
6.2(0.6)
|
0.000
|
6.7(0.9)
|
0.000
|
6.9(0.1)
|
0.002
|
0.000
|
Carbohydrate(%E)
|
-7.5(0.7)
|
0.000
|
-5.4(1.0)
|
0.000
|
-4.2(0.2)
|
0.000
|
0.000
|
1 Mean percentage and standard error (SE)in parentheses,2%E, percentage of dietary energy intake, 3 Values adjusted for, marital status, education, income, BMI, PA, smoking, drinking, 4 Significant trends in each sub-group across all survey years.5 Negative number means urban is smaller than rural.
A Comparison of the change values of urban-rural differences in dietary fat, protein, and carbohydrate intake in every two rounds of surveys is presented in Fig. 2. Generally, the variation in dietary fat, protein, and carbohydrate intake between urban and rural areas was greater in the former two rounds (2004 vs. 1991) than in the latter two rounds (2015 vs. 2004) (p < 0.001). Specifically, the variation of dietary energy intake decreased from 215.4 kcal/d to 43.3 kcal/d, from 436.5 kcal/d to 23.7 kcal/d, and from 234.5 kcal/d to 118.2 kcal/d in the eastern, central, and western districts, respectively. Moreover, the variation of fat intake decreased from − 6.9 g/d, 4.5 g/d and 1.4 g/d to -5.6 g/d,0.4 g/d and 0.9 g/d, protein intake decreased from 7.0 g/d,12.0 g/d and 7.4 g/d to 1.5 g/d,0.7 g/d and 0.5 g/d, and carbohydrate intake decreased from 58.1 g/d, 86.4 g/d and 48.8 g/d to 24.9 g/d,13.5 g/d and 41.9 g/d in the above three areas, respectively.