8 Anthropometric Variables

Anthropometric variables were collected and/or reported at several time points during development.

8.1 Body Mass Index (BMI)

Body Mass Index (BMI) was assessed throughout development, with 16 objective, clinic-based assessment points from ages 2-24 years, and 9 self-report or parent-report assessments of height and weight throughout puberty (ages 8-18). Table 8.1 provides information on specific variables and assessment timepoints.

Table 8.1: BMI-related variables across assessment points

Survey	Assessment-Type	Age Months Aim	Age Years Aim	Age Weeks	Age Months	Height	Weight	BMI	BMIZ	Respondent
cf	Clinic	25	2.08	cf014	NA	cf054	cf044	cf064	cf1143	NA
cf	Clinic	31	2.58	cf015	NA	cf055	cf045	cf065	cf1153	NA
cf	Clinic	37	3.08	cf016	NA	cf056	cf046	cf066	cf1163	NA
cf	Clinic	43	3.58	cf017	NA	cf057	cf047	cf067	cf1173	NA
cf	Clinic	49	4.08	cf018	NA	cf058	cf048	cf068	cf1183	NA
cf	Clinic	61	5.08	cf019	NA	cf059	cf049	cf069	cf1193	NA
f7	Clinic	90	7.50	f7003b	f7003c	f7ms010	f7ms026	f7ms026a	f7ms102	NA
pub1	SR/PR	97	8.08	pub194	pub195	pub103	pub104	pub105	NA	pub190
f8	Clinic	102	8.50	f8003b	f8003c	f8lf020	f8lf021	f8lf021a	f8lf027	NA
f9	Clinic	114	9.50	f9003b	f9003c	f9ms010	f9ms026	f9ms026a	f9ms202	NA
pub2	SR/PR	115	9.58	pub295b	pub295	pub203	pub204	pub205	NA	pub290
f10	Clinic	126	10.50	fd003b	fd003c	fdms010	fdms026	fdms026a	fdms102	NA
pub3	SR/PR	128	10.67	pub397b	pub397a	pub303	pub304	pub305	NA	pub395
f11	Clinic	138	11.50	fe003b	fe003c	fems010	fems026	fems026a	fems092	NA
pub4	SR/PR	140	11.67	pub497b	pub497a	pub403	pub404	pub505	NA	pub495
TF1	Clinic	150	12.50	ff0011b	ff0011a	ff2000	ff2030	ff2039	ff2034	NA
pub5	SR/PR	157	13.08	pub597b	pub597a	pub503	pub504	pub505	NA	pub595
TF2	Clinic	162	13.50	fg0011b	fg0011a	fg3100	fg3101	fg3139	fg3134	NA
pub6	SR/PR	175	14.58	pub697b	pub697a	pub603	pub604	pub605	NA	pub690, pub691, pub692
TF3	Clinic	186	15.50	fh0011b	fh0011a	fh3000	fh3000	fh3019	fh3014	NA
pub7	SR/PR	186	15.50	pub797b	pub797a	pub703	pub704	pub705	NA	pub790, pub791, pub792
pub8	SR/PR	192	16.00	pub897b	pub897a	pub803	pub804	pub804	NA	pub890, pub891, pub892
pub9	SR/PR	204	17.00	pub997b	pub997a	pub903	pub904	pub905	NA	pub990, pub991, pub992
TF4	Clinic	210	17.50	NA	FJ003a	FJMR020	FJMR022	FJMR022a	FJMR028	NA
F24	Clinic	288	24.00	NA	FKAR0010	FKMS1000	FKMS1030	FKMS1040	NA	NA

8.2 Scoring

For scoring purposes, all raw variables are included in cleaned data (renamed to follow appropriate naming conventions), along with derived variables which compute BMIz scores based on 2000 WHO reference data for all time points (including self-reported data). A ‘best available’ BMI (and accompanying BMIz score) within the past year at target ages 11.0, 14.0, 16.0, and 18.0 is also calculated. This ‘best available’ BMI data uses clinic data when available and self/parent-report data if clinic data is not available. This approach is used to maximize accuracy and coverage of data when BMI at a specified age is to be used for eating disorder diagnosis and/or employed as an analytic predictor.

8.3 Key Variables

BMIz scores are noted as:

BMIz_clinic.X Objective obtained BMI at clinic where X = age in months at time when assessment was targeted to be completed, rounded to one tenth.

BMIz_sr.X BMIz obtained by self- or parent-reported height and weight where X = age in months at time when assessment was targeted to be completed.

BMIz_bestavaial.Xy Best available BMIz with targeted capture in the 12 months prior to X where X = age in years