Table 1. Characteristics of participants according to the presence of underweight at 20 years old and/or at present.

	At 20 years old				P value
	Normal or Overweight		Underweight
	Present
	Normal or Overweight	Underweight	Normal or Overweight	Underweight
	Group 1	Group 2	Group 3	Group 4
n	521	74	103	51
Age	58.4 (8.5)	57.9 (8.1)	57.2 (9.3)	54.7 (9.5)	0.116
BMI at 20 years old
Median (25th–75th percentile)	20.5 (19.6–21.8)	19.7 (19.2–20.6)	17.7 (17.2–18.1)	18.0 (16.9–18.3)
Range	18.5–29.1	18.6–23.6	15.5–18.5	15.1–18.5
BMI at present
Median (25th–75th percentile)	21.4 (20.1–23.2)	17.7 (17.2–18.2)	20.2 (19.4–21.3)	17.7 (16.8–18.2)
Range	18.5–39.6	13.6–18.5	18.5–26.6	15.2–18.5
Menopause, %	78.7	79.7	77.7	64.7	0.142
Hyperthyroidism, %	2.7	1.4	1	2	0.683
Calcium supplement, %	4.4	6.8	9.7	2	0.096
Milk or yogurt intake, ml/week	1050 (600–1700)	1365 (560–1960)	1190 (500–1750)	990 (500–1400)	0.630
Walking time per day, %					0.305
less than 30 minutes	5.6	5.4	9.7	3.9
30–59 minutes	25.9	24.3	23.3	33.3
60–119 minutes	36.9	43.2	27.2	31.4
120 minutes or more	31.7	27	39.8	31.4
Smoking, %					0.354
Current, ex, never	2.3, 6.7, 91.0	1.4, 12.2, 86.5	0.0, 9.7, 90.3	3.9, 7.8, 88.2
Alcohol drinking, %					0.988
Current, ex, never	37.2, 2.7, 60.1	36.5, 2.7, 60.8	35.0, 1.9, 63.1	39.2, 3.9, 56.9

BMI, body mass index.

Normal or overweight: BMI ≥18.5 kg/m², Underweight: BMI <18.5 kg/m².

Continuous variables are presented as mean (standard deviation) or median (25th–75th percentile). Categorical variables are presented as percentage.