1980s, a large number of rural residents have migrated from their homes to cities in search of better employment opportunities. However, because of the unstable income, unfriendly settlement policies, and limited access to public services (such as education and health care) in host cities, most labor migrants leave their children at their homes in the countryside with another parent or other family members. According to the latest statistics, in 2015, 40.51 million rural children were left behind due to parental migration, accounting for 29.4% of all rural children and 15% of all children in China [2].The nutritional status of left-behind children, as one of their most important health outcomes, has drawn a lot of attention from researchers and policy-makers. A growing body of research in this field over the last three decades has yielded conflicting results. Most studies found that left-behind children were more likely to be stunted, underweight, or wasted compared with other children [3][4][5][6][7][8][9][10][11], but others found that left-behind children performed similarly to, or even better than, non-left-behind children on these anthropometric indicators [12][13][14][15]. In addition, some studies identified a higher risk of anemia among left-behind than non-left-behind children [16,17], but other work found no such difference [14]. A recent systematic review and meta-analysis of these studies done from 1994 to September 2018, 82% of which were conducted in China, found that, compared with non-left-behind children, left-behind children had a significantly increased risk of wasting and stunting, but a similar risk of underweight and anemia [18].Further research is necessary for consideration of the confusing findings and the possible shift in the impact of parental migration on child nutrition with socioeconomic development. In addition, despite numerous studies existing, some notable gaps in our knowledge remain. Firstly, most studies on nutrition of left-behind children focused on school-age children and few included infants and young children [18]. The findings from school-age children cannot be simply generalized to younger children because of the considerable differences in growth trajectories and living environment. Studies have provided strong evidence that undernutrition in the first 3 years of life has a long-term negative effect on an individual's health and development in subsequent childhood and adulthood, and intervention is problematic once this window has passed [19][20][21]. Therefore, further research is needed to take a clear picture of early childhood nutrition of left-behind children to allow policy-makers and health-care styles: analysis of factors influencing health of left-behind children. Qual Life Res 2016, 25(11):2921-2929. 7. Tian X, Ding C, Shen C, Wang H: Does parental migration have negative impact on the growth of left-behind children?-New evidence from longitudinal data in rural China. Int J Environ Res Public Health 2017, 14(11):1308. 8. Zhang N, Becares L, Chandola T: Does ...