Table 1. Overview of weight studies.

Study (Name, Year, Country, Quality rating)	Study aims	Sample	Study design	Outcome of interest/ theoretical framework	Main findings
Sowan & Stember (2000) [62]	To facilitate an understanding of the influence of the parental characteristics on the development of infant obesity.	630 infants (15 months) and their families. Recruited from six health care study sites.	Longitudinal prospective design: 1 months; 4 months; 7 months; 10 months; 14 months	BMI Obesity	Impact: no impact Grandmother living in the home was not significant predictor of child obesity.
USA
High quality				Web of causation model
Jain et al. (2001) [56]	To explore mothers’ perceptions about how they determine when a child is overweight and what barriers exist to prevent or manage childhood obesity.	18 low income mothers of preschool children (13 black and 5 white) who were at risk for later obesity.	3 focus groups	Weight	Impact: adverse Grandparents (on the whole) more permissive–causes difficulties–mothers feel undermined.
USA
High quality			Thematic analysis (though didn’t explicitly state this)
Gao et al. (2007) [53]	To identify effective obesity interventions in the Chinese literature.	3 Chinese and 9 international databases. Studies with: Intervention ˃3 months Control group and anthropometric measures	Systematic review	Interventions to reduce overweight & obesity. Studies that evaluated public health programmes aiming to prevent, control or reduce obesity or obesity-related factors in China.	Impact: adverse In Chinese families, many grandparents provide childcare assistance–preference for overfeeding. Grandparents as barrier to interventions.
China
Medium quality
Hawkins et al. (2008) [55]	To investigate factors related to early childhood overweight only among mothers in employment.	13,113 parents and children (aged 3 years)	Millennium Cohort Study—Longitudinal	Child overweight (including obesity)	Impact: no impact No difference in early childhood overweight between children cared for by informal arrangements (75% grandparents), and those cared for by their mother /mother’s partner AOR 1.02 (95%CI 0.92–1.13).
UK
High quality
Pearce et al. (2010) [59]	To explore the association between childcare and overweight.	Children born in UK between Sept 2000 and Jan 2002. Sweep 1 = 9 months–n = 18296 Sweep 2 = 3 years–n = 14630	Millennium Cohort Study—Longitudinal	Obesity	Impact: adverse Children cared for in informal childcare (75% grandparents) between age of 9 months and 3 years more likely to be overweight than those cared for only by a parent ARR 1.15 (95%CI 1.04–1.27), particularly if in full time care ARR 1.34 (95%CI 1.15–1.57). Increased risk only observed for those in informal childcare full time. Increased risk of overweight only significant in those care for by grandparents.
UK
High quality
Pocock et al. (2010) [60]	To synthesise qualitative research concerning parental perceptions regarding behaviours for preventing overweight and obesity in young children.	Qualitative papers with children under 12 as the focus.	Systematic review	Overweight and obesity	Impact: adverse Grandparents undermining parents by allowing children to eat what they want. Wish to avoid conflict with grandparents.
Various countries
Medium quality
Glassman et al. (2011) [54]	Latino parents’ perceptions of their ability to prevent obesity in children.	26 Latino parents of preschoolers at an NYC Headstart programme.	3 focus groups	Obesity prevention	Impact: adverse Grandparents providing less healthy food–children know they will get it from grandparents.
USA
Medium quality			Social cognitive theory used as themes for thematic analysis.	Social cognitive theory
Watanabe et al. (2011) [65]	To examine the effects of maternal employment and the presence of grandparents on lifestyles and overweight and obesity in Japanese pre-school children	2114 children aged 3–6 years who attended child care facilities and primary care givers.	Cross-sectional survey	Overweight/obesity	Impact: adverse Living in a three generational family associated positively with children’s overweight/ obesity, even after adjustment for maternal employment AOR 1.59 (95%CI 1.08–2.35)
Japan
High quality
Pulgarón et al. (2013) [61]	To evaluate the rate of Hispanic children who have grandparents involved in caretaking and whether grandparents’ involvement has a negative impact on feeding practices, children’s physical activity and BMI.	199 Hispanic children and parents from a Miami elementary school (5–12 years).	Cross-sectional survey	zBMI score	Impact: mixed/no impact No difference in zBMI for those who did and did not have a role in grandparent caring. Degree of grandparent involvement not correlated with child’s zBMI. zBMI positively correlated with parent and grandparent disagreement. For other Hispanic (non Cuban) children, grandparent caretaking had lower zBMI.
USA
Low quality
Tanskanen (2013) [63]	The association between maternal and paternal grandmothers’ childcare provision and early years overweight in the UK.	3 year old children from 15,109 families but 9000 in sample–where biological mother where living with child and biological father.	Millennium Cohort Study–Longitudinal information but second wave.	Overweight (including obesity)	Impact: adverse Where maternal grandmother provides most childcare, 20% more likely for child to be overweight. Not significant for paternal grandmother but underpowered. No differences based on mothers’ socioeconomic status.
UK
High quality
Toftemo et al. (2013) [64]	To explore parents’ views & experiences when health professionals identify their pre-school child as overweight.	Parents of 10 overweight children aged 2.5–5.5 years recruited at well child clinics in rural parts of Norway.	Indepth interviews	Overweight	Impact: mixed Grandparents undermine parents’ efforts to make changes—but some are excellent. Parents wanted support from grandparents. Children can be spoiled eg sweet foods. Need to educate grandparents.
Norway			Thematic analysis (systematic text condensation)
Medium quality
Li, Adab & Cheng (2014) [57]	To identify family & neighbourhood environmental correlates of overweight and related behaviour.	Parents of 497 Chinese 8–10 year olds in two Southern cities. Mix of socio-economic school backgrounds.	Cross-sectional study design	Overweight (including obesity)	Impact: adverse Children cared for by grandparents over twice as likely to be overweight/ obese AOR 2.03 (95%CI 1.19–3.47). Children living with at least two grandparents in house higher risk than those living with none AOR 1.72 (95%CI 1–2.94).
China			Routinely collected height and weight data.
Medium quality
Li et al. (2015) [58]	To investigate the impact of grandparents on the childhood obesity epidemic in China, in order to inform the development of culturally relevant childhood obesity intervention programmes.	Qualitative study: 25 parents & 24 grandparents of primary school children; 15 teachers & school nurses; 15 school catering staff; 4 head teachers	Mixed methods Focus groups and interviews Cross-sectional survey and measures	Obesity	Impact: adverse/ no impact Grandparents prefer grandchildren to be overweight, have poor knowledge of obesity health consequences and healthy diets, overfeed grandchildren, and limit activity.
China
Qualitative: High quality
			Thematic analysis
Sata et al. (2015) [66]	To examine the effect of caregiver differences on subsequent childhood habituation (between-meal eating habits, being overweight, and BMI).	Parents of children 3 years old in 1992. Follow ups when children aged 6, 12 and 22 (child completed at age 22).	Cohort study	Overweight BMI	Impact: no impact/ adverse Both boys and girls cared for by grandparents more likely to be overweight at age 3, but boys also more likely to be overweight at ages 6 and 12. Grandparent care was also associated with increases in BMI at ages 3, 6 and 12 for boys and girls.
Japan
Medium quality
Zong et al. (2015) [67]	To describe a wider spectrum of risk factors for obesity among preschool children (including being cared for by grandparents).	1996–1234 boys; 610 girls 2006–2290 boys; 1008 girls 3–7 year old children attending kindergarten (parents completed questionnaires).	Case control surveys in 1996 and 2006 –children who were obese matched to similar child who was not obese.	Obesity	Impact: no impact/ adverse 1996 –no impact of grandparent care. 2006 –grandparent care increases likelihood of children being obese AOR 1.44 (95%CI 1.05–1.97);
China
Medium quality
Ikeda et al. (2017) [68]	To track the likelihoods of childhood overweight and obesity from living in a household with grandparents from early childhood to school age.	43,046 children aged 2.5, followed up multiple times until age 13. Parent-complete until age 11	Cohort study	Overweight & obesity	Impact: adverse/ no impact Living with grandparents increased the odds of boys being overweight or obese from ages 5 to 13, and in girls from ages 5 and 8–12
Japan
Medium quality
Pulgarón et al. (2016) [32]	To gather and synthesise research findings on the effects of grandparent involvement on children’s physical health outcomes.	26 papers published between 1994–2014 reporting data on child health, well-being and safety outcomes.	Literature review	Weight	Impact: mixed 5/6 studies found adverse impact of grandparent involvement on child weight.
Various
Medium quality