TABLE 3.
Weight change over 4-y periods according to quintiles of change in the hPDI and uDPI1
| Q1 | Q2 | Q3 | Q4 | Q5 | Per 1-SD increase | P value2 | |
|---|---|---|---|---|---|---|---|
| hPDI | |||||||
| NHS | |||||||
| Median index change | −8 | −4 | 0 | 3 | 8 | ||
| Mean weight change, lb | 4.3 | 3.3 | 2.8 | 2.1 | 0.69 | ||
| Age-adjusted model, lb | 1.75 (1.58, 1.91) | 0.53 (0.37, 0.69) | Ref | −0.76 (−0.91, −0.60) | −2.13 (−2.30, −1.96) | −1.40 (−1.47, −1.34) | <0.001 |
| Multivariable model, lb | 1.71 (1.54, 1.87) | 0.51 (0.36, 0.67) | Ref | −0.73 (−0.88, −0.58) | −2.10 (−2.27, −1.94) | −1.39 (−1.45, −1.33) | <0.001 |
| NHS2 | |||||||
| Median index change | −8 | −3 | 0 | 3 | 9 | ||
| Mean weight change, lb | 6.6 | 5.3 | 4.5 | 3.7 | 2.0 | ||
| Age-adjusted model, lb | 2.25 (2.10, 2.40) | 0.75 (0.60, 0.89) | Ref | −0.89 (−1.03, −0.74) | −2.53 (−2.69, −2.38) | −1.77 (−1.83, −1.71) | <0.001 |
| Multivariable model, lb | 2.19 (2.04, 2.34) | 0.66 (0.52, 0.81) | Ref | −0.88 (−1.03, −0.74) | −2.49 (−2.65, −2.34) | −1.74 (−1.80, −1.68) | <0.001 |
| HPFS | |||||||
| Median index change | −8 | −3 | 0 | 4 | 9 | ||
| Mean weight change, lb | 3.4 | 2.5 | 2.1 | 1.3 | 0.29 | ||
| Age-adjusted model | 1.46 (1.24, 1.67) | 0.52 (0.32, 0.71) | Ref | −0.78 (−0.99, −0.58) | −1.83 (−2.04, −1.62) | −1.26 (−1.34, −1.18) | <0.001 |
| Multivariable model | 1.45 (1.24, 1.66) | 0.54 (0.35, 0.74) | Ref | −0.71 (−0.91, −0.51) | −1.85 (−2.06, −1.64) | −1.25 (−1.33, −1.17) | <0.001 |
| Pooled (fixed-effects model) | |||||||
| Age-adjusted model | 1.90 (1.80, 2.00)3 | 0.62 (0.52, 0.71) | Ref | −0.82 (−0.91, −0.72) | −2.23 (−2.33, −2.13)3 | −1.52 (−1.55, −1.48)3 | <0.0013 |
| Multivariable model | 1.86 (1.76, 1.96)3 | 0.58 (0.49, 0.67) | Ref | −0.79 (−0.88, −0.70) | −2.21 (−2.31, −2.11)3 | −1.50 (−1.53, −1.46)3 | <0.0013 |
| uPDI | |||||||
| NHS | |||||||
| Median index change | −7 | −3 | 0 | 3 | 7 | ||
| Mean weight change, lb | 1.9 | 2.4 | 2.7 | 2.9 lbs | 3.3 | ||
| Age-adjusted model, lb | −0.97 (−1.13, −0.81) | −0.33 (−0.49, −0.17) | Ref | 0.25 (0.09, 0.41) | 0.84 (0.68, 1.01) | 0.66 (0.60, 0.72) | <0.001 |
| Multivariable model, lb | −0.90 (−1.06, −0.74) | −0.15 (−0.31, 0.01) | Ref | 0.44 (0.28, 0.60) | 0.88 (0.72, 1.04) | 0.66 (0.60, 0.72) | <0.001 |
| NHS2 | |||||||
| Median index change | −8 | −4 | −1 | 2 | 7 | ||
| Mean weight change, lb | 3.1 | 4.0 | 4.5 | 4.9 | 5.6 | ||
| Age-adjusted model, lb | −1.61 (−1.77, −1.46) | −0.58 (−0.72, −0.43) | Ref | 0.44 (0.29, 0.59) | 1.43 (1.27, 1.58) | 1.09 (1.03, 1.15) | <0.001 |
| Multivariable model, lb | −1.56 (−1.71, −1.40) | −0.51 (−0.65, −0.37) | Ref | 0.48 (0.34, 0.63) | 1.47 (1.32, 1.62) | 1.10 (1.04, 1.16) | <0.001 |
| HPFS | |||||||
| Median index change | −7 | −3 | 0 | 3 | 7 | ||
| Mean weight change, lb | 1.3 | 1.8 | 2.1 | 2.1 | 2.3 | ||
| Age-adjusted model, lb | −0.90 (−1.12, −0.68) | −0.28 (−0.48, −0.08) | Ref | 0.01 (−0.19, 0.21) | 0.35 (0.13, 0.57) | 0.43 (0.36, 0.51) | <0.001 |
| Multivariable model, lb | −0.93 (−1.15, −0.71) | −0.29 (−0.49, −0.10) | Ref | 0.02 (−0.18, 0.22) | 0.34 (0.12, 0.55) | 0.43 (0.36, 0.51) | <0.001 |
| Pooled (fixed-effects model) | |||||||
| Age-adjusted model, lb | −1.22 (−1.32, −1.13)3 | −0.42 (−0.52, −0.33)3 | Ref | 0.28 (0.18, 0.37)3 | 0.99 (0.88, 1.09)3 | 0.79 (0.75, 0.82)3 | <0.0013 |
| Multivariable model, lb | −1.18 (−1.28, −1.08)3 | −0.34 (−0.43, −0.24)3 | Ref | 0.36 (0.27, 0.46)3 | 1.01 (0.91, 1.11)3 | 0.79 (0.75, 0.82)3 | <0.0013 |
Values are weight change in lb (95% CI). Given that most participants gained weight over 4-y intervals, inverse associations of the diet indices with weight change (i.e., negative values) should be interpreted as “less weight gain,” not as “weight loss.” We used multivariable generalized linear regression models (with unstructured correlation matrix and robust variance) to conduct this analysis. Multivariable model: adjusted for age, questionnaire cycle, baseline BMI, change in smoking status, baseline and change in physical activity, hours of sleep, hours of sitting and watching television, change in alcohol consumption, change in margarine intake, and for women only, baseline parity, menopausal status, postmenopausal hormone use, and oral contraceptive use (NHS2 only). 1 lb = 0.45 kg. hPDI, healthful plant-based diet index; HPFS, Health Professionals Follow-up Study; NHS, Nurses’ Health Study; uPDI, unhealthful plant-based diet index.
P value obtained from per 1-SD increase in β coefficient.
P value for Q statistic for heterogeneity <0.05, indicating statistically significant heterogeneity in results among the 3 studies.