Table 1.
Characteristics of 1,587 individual twins stratified by tertile of Restraint Scale score
| Low (≤11) | Intermediate (12 ≤16) | High (>16) | P valuea | |
|---|---|---|---|---|
| Number, N (%) | 610 (38) | 518 (33) | 459 (29) | |
| Gender | <0.001 | |||
| Male, N (%) | 274 (54) | 138 (27) | 91 (18) | |
| Female, N (%) | 336 (31) | 380 (35) | 368 (34) | |
| Age, mean years (s.d.) | 33 (13) | 36 (13) | 38 (14) | < 0.001 |
| White, N (%) | 547 (90) | 463 (89) | 409 (89) | 0.9 |
| Education | 0.02 | |||
| High school or less, N (%) | 78 (13) | 55 (11) | 40 (9) | |
| Some college or technical school, N (%) | 267 (44) | 209 (40) | 227 (49) | |
| College or graduate, N (%) | 265 (43) | 254 (49) | 192 (42) | |
| Physical activity, mean min/week (s.d.) | 133 (92) | 137 (91) | 136 (92) | 0.8 |
| Ever smoked, N (%) | 162 (27) | 169 (33) | 171 (37) | 0.003 |
| Current smoking | 0.09 | |||
| None, N (%) | 513 (84) | 441 (85) | 378 (83) | |
| Some days, N (%) | 19 (3) | 29 (6) | 28 (6) | |
| Every day, N (%) | 77 (13) | 48 (9) | 52 (11) | |
| Time between surveys, mean years (s.d.) | 3.0 (1.0) | 3.2 (1.0) | 3.2 (0.9) | 0.01 |
| Number of MZ pairs, N (%) | 443 (73) | 381 (74) | 329 (72) | 0.8 |
| BMI category | <0.001 | |||
| Underweight (<18.5 kg/m2), N (%) | 22 (4) | 11 (2) | 7 (1.5) | |
| Normal weight (18.5–24.9 kg/m2), N (%) | 459 (75) | 284 (55) | 161 (35) | |
| Overweight (25–29.9 kg/m2), N (%) | 103 (17) | 147 (28) | 137 (30) | |
| Obese (≥30 kg/m2), N (%) | 26 (4) | 76 (15) | 154 (34) | |
| Lifetime maximum weight, mean pounds (s.d.) | 157 (31) | 173 (40) | 195 (49) | <0.001 |
| Number of attempts to lose weight in past year | <0.001 | |||
| None, N (%) | 465 (78) | 173 (34) | 52 (11) | |
| 1–2 times, N (%) | 87 (15) | 161 (32) | 111 (25) | |
| 3–5 times, N (%) | 14 (2) | 65 (13) | 71 (16) | |
| >5 times, N (%) | 3 (0.5) | 22 (4) | 34 (7.5) | |
| Was trying to lose weight continuously, N (%) | 30 (5) | 87 (17) | 184 (41) |
MZ, monozygotic.
a
P values were calculated by Wald tests from regression models using generalized estimating equations estimation and robust s.e. to account for the clustered nature of the twin data.