TABLE 2.
Clinical characteristics of the study cohort1
| Characteristic | Total (n = 77) | Spendthrift (n = 38) | Thrifty (n = 39) | P value |
|---|---|---|---|---|
| Male, n (%) | 63 (81.8) | 31 (81.6) | 32 (82.1) | 0.96 |
| Ethnicity, n (%) | 0.43 | |||
| African American | 18 (23.4) | 11 (29.0) | 7 (18.0) | |
| Caucasian | 26 (33.8) | 10 (26.3) | 16 (41.0) | |
| Native American | 23 (29.9) | 11 (29.0) | 12 (30.8) | |
| Hispanic | 10 (13.0) | 6 (15.8) | 4 (10.3) | |
| Age, y | 37.2 ± 10.2 (18, 55) | 36.7 ± 10.2 (18, 55) | 37.7 ± 10.3 (19, 53) | 0.66 |
| Body composition measures | ||||
| Height, cm | 173 ± 8 (157, 196) | 173 ± 8 (157, 196) | 172 ± 7 (157, 185) | 0.54 |
| Body weight, kg | 78.9 ± 14.1 (47.5, 127.1) | 79 ± 14 (56, 127.1) | 78.9 ± 14.3 (47.5, 107.8) | 0.97 |
| BMI, kg/m2 | 26.4 ± 4.3 (17.8, 44) | 26.3 ± 4.2 (20.6, 44) | 26.5 ± 4.5 (17.8, 39.1) | 0.77 |
| Body fat, % | 27.7 ± 9.4 (6.9, 53.8) | 27.7 ± 11.2 (7.3, 53.8) | 27.6 ± 7.5 (6.9, 52.8) | 0.96 |
| FM, kg | 22.4 ± 10.2 (4.9, 56.9) | 22.5 ± 11.4 (4.9, 54.1) | 22.2 ± 9.1 (5.9, 56.9) | 0.88 |
| FFM, kg | 56.6 ± 9.7 (33.9, 79.4) | 56.4 ± 9.7 (34.2, 77) | 56.7 ± 9.9 (33.9, 79.4) | 0.91 |
| Energy expenditure measures during energy balance | ||||
| RQ, ratio | 0.86 ± 0.04 (0.76, 1.02) | 0.87 ± 0.03 (0.8, 0.94) | 0.86 ± 0.04 (0.76, 1.02) | 0.47 |
| 24EE, kcal/d | 2015 ± 306 (1427, 2810) | 1960 ± 308 (1502, 2810) | 2070 ± 299 (1427, 2732) | 0.11 |
| Adjusted 24EE,2 kcal/d | 2015 ± 125 (1676, 2232) | 1960 ± 123 (1676, 2212) | 2070 ± 103 (1837, 2232) | <0.0001 |
| SLEEP, kcal/d | 1594 ± 246 (1131, 2303) | 1539 ± 220 (1193, 2227) | 1649 ± 261 (1131, 2303) | 0.049 |
| Adjusted SLEEP,2 kcal/d | 1594 ± 113 (1355, 1892) | 1548 ± 93 (1355, 1730) | 1640 ± 113 (1446, 1892) | 0.0002 |
| EE0, kcal/15 h | 1339 ± 203 (969, 1930) | 1310 ± 213 (1025, 1930) | 1366 ± 191 (969, 1733) | 0.22 |
| Adjusted EE0,2 kcal/15 h | 1339 ± 88 (1123, 1520) | 1309 ± 92 (1123, 1520) | 1367 ± 74 (1197, 1509) | 0.003 |
| AFT, kcal/15 h | 343 ± 103 (145, 624) | 349 ± 110 (171, 624) | 337 ± 97 (145, 557) | 0.62 |
| Adjusted AFT,2 kcal/15 h | 343 ± 83 (181, 553) | 343 ± 81 (208, 553) | 342 ± 86 (181, 503) | 0.96 |
| SPA, % of time | 5.9 ± 3.4 (0.7, 16.4) | 6.3 ± 3.9 (1.2, 16.4) | 5.6 ± 2.7 (0.7, 15.5) | 0.41 |
| 24-h energy intake, kcal/d | 2051 ± 304 (1512, 2921) | 2008 ± 313 (1529, 2921) | 2092 ± 293 (1512, 2709) | 0.23 |
| Energy balance, % | 1.9 ± 4.3 (−7.3, 19.7) | 2.6 ± 4.1 (−3.8, 19.7) | 1.2 ± 4.5 (−7.3, 16.4) | 0.17 |
| Energy expenditure measures during 24-h fasting | ||||
| RQ, ratio | 0.79 ± 0.03 (0.71, 0.9) | 0.79 ± 0.03 (0.73, 0.88) | 0.79 ± 0.03 (0.71, 0.9) | 0.88 |
| 24EE, kcal/d | 1851 ± 261 (1287, 2655) | 1858 ± 275 (1429, 2655) | 1845 ± 249 (1287, 2390) | 0.82 |
| Adjusted 24EE,2 kcal/d | 1851 ± 105 (1619, 2103) | 1869 ± 107 (1639, 2103) | 1834 ± 100 (1619, 2051) | 0.14 |
| Δ adjusted 24EE fromenergy balance tofasting,2 kcal/d | −164 ± 89 (−376, 104) | −91 ± 59 (−177, 104) | −236 ± 44 (−376, −178) | <0.0001 |
| SPA, % of time | 5.5 ± 3.2 (0.4, 18.3) | 5.4 ± 3.5 (1.1, 18.3) | 5.5 ± 3 (0.4, 12.7) | 0.88 |
Values are presented as mean ± SD (minimum, maximum) unless otherwise indicated. Classification of participants into the spendthrift or thrifty metabolic group was based on the median value of decrease in adjusted 24EE from energy balance during 24-h fasting (−177 kcal/d), such that thrifty participants were those with a greater-than-median decrease in 24EE. Differences between thrifty and spendthrift metabolic groups were assessed by Student unpaired t test for continuous variables and by χ2 test for categorical variables.
Adjusted 24-h energy expenditure was calculated by adding the average value calculated in the whole cohort to the residual values obtained from linear regression analysis with covariates age, sex, ethnicity, FM, FFM, SPA, ambient temperature, and calorimeter room. AFT, awake-fed thermogenesis; EE0, EE in the inactive, awake state; FM, fat mass; FFM, fat-free mass; RQ, respiratory quotient; SLEEP, sleeping metabolic rate; SPA, spontaneous physical activity; 24EE, 24-h energy expenditure.