**Accessing the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 (ECLS-K) data**

Data used in the analyses were accessed from the National Center for Education Statistics: https://nces.ed.gov/pubsearch/pubsinfo.asp?pubid=2009005. The Class of 1998-99 can be accessed here: https://nces.ed.gov/ecls/dataproducts.asp. 

This study used data from the 5th grade survey wave. 

**Accessing the Millennium Cohort Study (MCS) data**
he Millennium Cohort Study (MCS), known as ‘Child of the New Century’ to cohort members and their families, is following the lives of around 19,000 young people born across England, Scotland, Wales and Northern Ireland in 2000-01.

Data may be obtained by registering here: http://www.data-archive.ac.uk/sign-up

If you are from a UK institution of higher or further education, or your institution uses federated access management, you can login immediately. Otherwise, you need to apply for a 
UK Data Archive username and password.

When these have been issued to you, log in via the UK federation link on the UK Data Service login page, selecting the UK Data Archive as the organization you wish to sign in with.

The first time you login you will be required to complete a short registration form. You can find and access the Millennium Cohort Study using Discover, the UK Data Service search interface. 

Once you select MCS, you need to register a use of the data. This includes a brief description of how you intend to use the data. 

This study used Parent interviews, Child BMI assessments, and Derived files from MCS5 and some demographics from MCS1 and MCS2. 


**ECLS K analyses**

‘Data cleaning ECLS-K’ file was used to construct the variables for analyses and ‘Analyses ECLS-K’ file implemented the results. Syntax was constructed in SPSS version 25.

**MCS analyses**

‘MCS analyses’ file was used to implement the results for MCS tables. Syntax was constructed in STATA version 15.1.