Table 1.

Characteristics of study variables (unweighted) comparing underweight and overweight or obese with healthy body mass index (BMI) categories

	Healthy BMI	Underweight BMI		Overweight/Obese BMI		Total (n = 93 429)
	(n = 34 244)	(n = 1634)	P	(n = 57 551)	P
Age (25/50/75th percentile)	28/42/54	19/27/42	<0.001	39/48/63	<0.001	34/44/60
Male (%)	38.3	31.5	<0.001	48.6	<0.001	44.5
Lesbian/Gay identity (%)	1.3	2.0	0.02	1.1	<0.001	1.2
Bisexual identity (%)	1.0	1.6	0.03	0.9	0.008	0.9
Other identity (%)	0.6	1.3	0.001	0.8	0.001	0.7
Ethnic minority (%)	9.9	17.9	<0.001	6.7	<0.001	8.1
Degree level education (%)	30.0	20.6	<0.001	23.9	<0.001	26.1
Smoker (%)	26.0	37.6	<0.001	20.4	<0.001	22.7
Longstanding illness/disability (%)	28.9	31.3	0.03	42.4	<0.001	37.3
Married/cohabiting (%)	57.6	32.0	<0.001	68.1	<0.001	63.6

Notes: Underweight BMI is defined as a BMI value <18.5 kg/m². Healthy BMI is defined as a BMI value in the range 18.5–24.99 kg/m². Overweight BMI is defined as a BMI value in the range 25–29.99 kg/m². Obese BMI is defined as a BMI value ≥30 kg/m². P values are for comparisons of each BMI category separately with the healthy BMI category, and are estimated from chi-square tests. The P values for difference in age were calculated using t-tests.